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Scientists Urge Europe to Stick With “Armageddon”-style Asteroid Mission

September 22nd, 2017

For decades, scientists have known that in near-Earth space there are thousands of comets and asteroids that periodically cross Earth’s orbit. These Near-Earth Objects (NEOs) are routinely tracked by NASA’s Center for Near Earth Object Studies (CNEOS) to make sure that none pose a risk of collision with our planet. Various programs and missions have also been proposed to divert or destroy any asteroids that might pass too closely to Earth in the future.

One such mission is the Asteroid Impact & Deflection Assessment (AIDA), a collaborative effort between NASA and the European Space Agency (ESA). Recently, the ESA announced that it would be withdrawing from this mission due to budget constraints. But this past Wednesday (Sept. 20th), during the European Planetary Science Conference in Riga, a group of international scientists urged them to reconsider.

In addition to NASA and the ESA, AIDA was designed with assistance from the Observatoire de la Côte d´Azur (OCA), and the Johns Hopkins University Applied Physics Laboratory (JHUAPL). To test possible asteroid deflection techniques, the mission intends to send a spacecraft to crash into the tiny moon of the distant asteroid named Didymos (nicknamed “Didymoon”) by 2022 to alter its trajectory.

Artist’s impression of the path DART will take to reach the asteroid Didymos. Credit: NASA

This mission would be a first for scientists, and would test the capabilities of space agencies to divert rocks away from Earth’s orbit. NASA’s contribution to this mission is known as the Double Asteroid Redirection Test (DART), the spacecraft which would be responsible for crashing into Didymoon. Plans for this spacecraft recently entered Phase B, having met with approval, but still in need of further development.

The plan was to mount DART on an already planned commercial or military launch, and would then be placed in geosynchronous orbit between December 2020 and May 2021. It would then rely on a NEXT-C ion engine to push itself beyond the Moon and reach an escape point to depart the Earth-Moon system, eventually making its way to Didymos and Didymoon.

Europe’s contribution to the mission was known as the Asteroid Impact Mission (AIM), which would involve sending a small craft close to Didymos to observe the crash and conduct research on the asteroid’s moon. Unfortunately, this aspect of the mission suffered a setback when space ministers from the ESA’s 22 member states rejected a €250 million ($300 million USD) request for funding last December.

However, during the European Planetary Science Congress – which will be taking place from September 17th to 22nd in the Latvian capital of Riga – scientists took the opportunity to advise the mission’s European partners to get back on board. As they emphasized, this mission – which is a dry-run for future asteroid redirect missions – is crucial if space agencies hope to develop the capacity to protect Earth from hazardous NEOs.

ESA’s Asteroid Impact Mission, a candidate mission due for launch in 2020, will map the smaller body of the Didymos binary asteroid system down to 1 m resolution following its arrival in 2022. Credit: ESA

Andrew Cheng from JHUAPL is the project scientist for the DART mission. As he told the AFP at the European Planetary Science Congress, “This is the kind of disaster that could be a tremendous catastrophe.” He also stressed that unlike other natural disasters, an asteroid strike “is something that the world is able to defend. We can do something.”

But before that can happen, the methods need to be further developed, tested and refined. Hence why Didymoon was selected as the target for the AIDA mission. Whereas the meteor that exploded over the Russian town of Chelyabinsk in 2013 was just 20 meters across (65 feet), but still injured 1600 people, Didymoon measures about 160 meters (525 feet) in diameter.

It is estimated that if this asteroid struck Earth, the resulting impact would be as powerful as a 400 megatonne blast. To put that in perspective, the most powerful thermonuclear device ever built – the Soviet Tsar Bomba – had a yield of 50 megatonnes. Hence, the smaller companion of this binary asteroid, if it struck Earth, would have an impact 80 times greater than the most powerful bomb ever built by humans.

In addition to advocating that the ESA remain committed to the mission, European scientists at the conference also proposed an altered, more cost-effective alternative for AIM. This alternative called for a miniaturized version of the AIM craft that would be equipped with just a camera, forgoing a lander and radars designed to probe Didymoon’s internal structure.

Simulated image of the Didymos system, derived from photometric lightcurve and radar data. Credits: Naidu et al./AIDA Workshop (2016)

According to Patrick Michel, the science lead for the AIM mission, this revised mission would cost about €210 million ($250 million USD). But as he also noted, this would require that the AIM part of the mission be delayed. While it would still conduct crucial measurements of Didymoon, it would not be part of the AIDA mission if NASA decides to stick with its original timeline.

“The main point of the mission was to measure the mass of the object, because this is how you really measure the deflection,” he said. “Two or three years (after impact), these things won’t change. Of course it’s better… that we have the two at the same time. But we found something I think that still works and allows to relax the very tight schedule.”

In the meantime, Jan Woerner – the head of the European Space Agency – indicated that the ESA would be moving forward with the new proposal when the next ministerial meeting takes place in 2019. As he told the AFP via email:

“It is important for humanity, as a species we have the means today to deflect an asteroid. We know it will happen, one day sooner or later. It’s not a question of if, but when. We have never tested asteroid deflection and there is no way we can test in (the) laboratory. We need to know if our models are correct, (whether) our simulations work as expected.”

In the end, it remains to be seen if the AIDA mission will see one or two missions traveling to Didymoon by 2022. Obviously, it would be better if both mission happened simultaneously, as the AIM mission will be capable of obtaining information DART will not. Much of that information has to do with with studying the effects of the collision up close and as they happen.

But regardless of how this mission unfolds, it is clear that space agencies from around the world are dedicated to developing techniques for protecting Earth from asteroids that pose a collision hazard. Between NASA, the ESA, and their many institutional partners and private contractors, multiple methods are being developed to divert or destroy oncoming space rocks before they hit us.

However, I’m pretty sure not one of them involves sending a bunch of miners with minimal training into space to plant a nuke inside an asteroid. That would just be silly on its face!

And be sure to check out this video that details the AIDA and Asteroid Impact Mission, courtesy of ESA:

 

Further Reading: AFP

 

The post Scientists Urge Europe to Stick With “Armageddon”-style Asteroid Mission appeared first on Universe Today.



NASA’s OSIRIS-REx Asteroid Sampler Slingshots Around Earth Friday, Sept. 22 – Catch It If You Can!

September 22nd, 2017

Artist’s concept shows the OSIRIS-REx spacecraft passing by Earth on Sept. 22, 2017. Credits: NASA’s Goddard Space Flight Center/University of Arizona

KENNEDY SPACE CENTER, FL – Barely a year after NASA’s OSIRIS-REx robotic asteroid sampler launched on a trailblazing mission to snatch a soil sample from a pristine asteroid and return it to Earth for research analysis, the probe is speeding back home for a swift slingshot around our home planet on Friday Sept. 22 to gain a gravity assist speed boost required to complete its journey to the carbon rich asteroid Bennu and back.

As it swings by Earth NASA’s first ever asteroid sample return mission, OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security – Regolith Explorer), will pass only 11,000 miles (17,000 kilometers) above Earth just before 12:52 p.m. EDT on Friday.

And NASA is asking the public to try and ‘Catch It If You Can’ – by waving hello and/or taking snapshots during and after the probes high speed flyby.

Plus you can watch NASA Facebook Live event at Noon Friday: https://www.facebook.com/NASAGoddard/

OSIRIS-REx will be approaching Earth at a velocity of about 19,000 mph on Friday as it begins flying over Australia during the Earth Gravity Assist (EGA) maneuver.

Since blastoff from the Florida Space Coast on Sept. 8, 2016 the probe has already racked up almost 600 million miles on its round trip journey from Earth and back to set up Friday’s critical gravity assist maneuver to Bennu and back.

As OSIRIS-REx continues along its flight path the spacecraft will reach its closest point to Earth over Antarctica, just south of Cape Horn, Chile. It will gain a velocity boost of about 8400 mph.

The spacecraft will also conduct a post flyby science campaign by collecting images and science observations of Earth and the Moon four hours after closest approach to calibrate its five science instruments.

NASA’s OSIRIS-REx asteroid sampling spacecraft, return capsule and payload fairings inside the Payloads Hazardous Servicing Facility high bay at NASA’s Kennedy Space Center is being processed for Sep. 8, 2016 launch to asteroid Bennu from Cape Canaveral, FL. Credit: Ken Kremer/kenkremer.com

The allure of Bennu is that it is a carbon rich asteroid – thus OSIRIS-REx could potentially bring back samples infused with the organic chemicals like amino acids that are the building blocks of life as we know it.

“We are interested in that material because it is a time capsule from the earliest stages of solar system formation,” OSIRIS-Rex Principal Investigator Dante Lauretta told Universe Today in a prelaunch interview with the spacecraft in the cleanroom at NASA’s Kennedy Space Center.

The do or die gravity assist plunge is absolutely essential to set OSIRIS-REx on course to match the asteroid’s path and speed when it reaches the vicinity of asteroid Bennu a year from now in October 2018.

“The Earth Gravity Assist is a clever way to move the spacecraft onto Bennu’s orbital plane using Earth’s own gravity instead of expending fuel,” says Lauretta, of the University of Arizona, Tucson.

Just how close to Earth will OSIRIS-REx be during its flyby on Friday? The spacecraft will come within 11,000 miles (17,000 km) of the Earth’s surface as it passes over Antarctica at 12:52 a.m. EDT. on Sept. 22, 2017. Credits: NASA’s Goddard Space Flight Center/University of Arizona

Bennu’s orbit around the Sun is tilted at a six-degree inclination with respect to Earth’s orbital plane.

The asteroid is 1,614-foot (500 m) in diameter and crosses Earth’s orbit around the sun every six years.

Numerous NASA spacecraft – including NASA’s just completed Cassini mission to Saturn – utilize gravity assists around a variety of celestial bodies to gain speed and change course to save vast amounts of propellant and time in order to accomplish science missions and visit additional target objects that would otherwise be impossible.

The flyby will be a nail-biting time for NASA and the science team because right afterwards the refrigerator sized probe will be out of contact with engineers – unable to receive telemetry for about an hour.

“For about an hour, NASA will be out of contact with the spacecraft as it passes over Antarctica,” said Mike Moreau, the flight dynamics system lead at Goddard, in a statement.

“OSIRIS-REx uses the Deep Space Network to communicate with Earth, and the spacecraft will be too low relative to the southern horizon to be in view with either the Deep Space tracking station at Canberra, Australia, or Goldstone, California.”

NASA says the team will regain communication with OSIRIS-REx roughly 50 minutes after closest approach over Antarctica at about 1:40 p.m. EDT.

The post flyby science campaign is set to begin at 4:52 p.m. EDT, Friday, Sept. 22.

United Launch Alliance Atlas V rocket lifts off from Space Launch Complex 41 at Cape Canaveral Air Force Station carrying NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, or OSIRIS-REx spacecraft on the first U.S. mission to sample an asteroid, retrieve at least two ounces of surface material and return it to Earth for study. Liftoff was at 7:05 p.m. EDT on September 8, 2016 in this remote camera view taken from inside the launch pad perimeter. Note the newly install crew access arm and white room for astronaut flights atop Atlas starting in early 2018. Credit: Ken Kremer/kenkremer.com

The OSIRIS-Rex spacecraft originally departed Earth atop a United Launch Alliance Atlas V rocket under crystal clear skies on September 8, 2016 at 7:05 p.m. EDT from Space Launch Complex 41 at Cape Canaveral Air Force Station, Florida.

Everything with the launch went exactly according to plan for the daring mission boldly seeking to gather rocks and soil from carbon rich Bennu.

View of science instrument suite and TAGSAM robotic sample return arm on NASA’s OSIRIS-REx asteroid sampling spacecraft inside the Payloads Hazardous Servicing Facility at NASA’s Kennedy Space Center. Probe is slated for Sep. 8, 2016 launch to asteroid Bennu from Cape Canaveral Air Force Station, FL. Credit: Ken Kremer/kenkremer.com

OSIRIS-Rex is equipped with an ingenious robotic arm named TAGSAM designed to collect at least a 60-gram (2.1-ounce) sample and bring it back to Earth in 2023 for study by scientists using the world’s most advanced research instruments.

“The primary objective of the OSIRIS-Rex mission is to bring back pristine material from the surface of the carbonaceous asteroid Bennu,” OSIRIS-Rex Principal Investigator Dante Lauretta told me in the prelaunch interview in the KSC cleanroom with the spacecraft as the probe was undergoing final launch preparations.

“We are interested in that material because it is a time capsule from the earliest stages of solar system formation.”

“It records the very first material that formed from the earliest stages of solar system formation. And we are really interested in the evolution of carbon during that phase. Particularly the key prebiotic molecules like amino acids, nucleic acids, phosphates and sugars that build up. These are basically the biomolecules for all of life.”

1 day to Earth flyby for OSIRIS-Rex

NASA and the mission team is also inviting the public to get engaged by participating in the Wave to OSIRIS-REx social media campaign.

“Individuals and groups from anywhere in the world are encouraged to take photos of themselves waving to OSIRIS-REx, share them using the hashtag #HelloOSIRISREx and tag the mission account in their posts on Twitter (@OSIRISREx) or Instagram (@OSIRIS_REx).

Participants may begin taking and sharing photos at any time—or wait until the OSIRIS-REx spacecraft makes its closest approach to Earth at 12:52p.m. EDT on Friday, Sept. 22.”

The probe’s flight path during the flyby will pass through the ring of numerous satellites orbiting in geosynchronous orbit, but none are expected to be within close range.

Members of the OSIRIS-REx mission team celebrate the successful spacecraft launch on Sept. 8, 2016 atop ULA Atlas V at the post-launch briefing at the Kennedy Space Center, FL. Principal Investigator Dante Lauretta is 4th from right, NASA Planetary Science Director Jim Green is center, 5th from left. Credit: Ken Kremer/kenkremer.com

Watch for Ken’s continuing onsite NASA mission and launch reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

Dr Dante Lauretta, principal investigator for OSIRIS-REx at the University of Arizona, Tucson, and Dr. Ken Kremer, Universe Today point to NASA’s OSIRIS-REx asteroid sampling spacecraft inside the Payloads Hazardous Servicing Facility at the Kennedy Space Center on Aug. 20, 2016. Credit: Ken Kremer/kenkremer.com

The post NASA’s OSIRIS-REx Asteroid Sampler Slingshots Around Earth Friday, Sept. 22 – Catch It If You Can! appeared first on Universe Today.



New Study Says a Fast Radio Burst Happens Every Second in the Universe

September 22nd, 2017

When astronomers first noted the detection of a Fast Radio Burst (FRB) in 2007 (aka. the Lorimer Burst), they were both astounded and intrigued. This high-energy burst of radio pulses, which lasted only a few milliseconds, appeared to be coming from outside of our galaxy. Since that time, astronomers have found evidence of many FRBs in previously-recorded data, and are still speculated as to what causes them.

Thanks to subsequent discoveries and research, astronomers now know that FRBs are far more common than previously thought. In fact, according to a new study by a team of researchers from the Harvard-Smithsonian Center for Astrophysics (CfA), FRBs may occur once every second within the observable Universe. If true, FRBs could be a powerful tool for researching the origins and evolution of the cosmos.

The study, titled “A Fast Radio Burst Occurs Every Second throughout the Observable Universe“, recently appeared in The Astrophysical Journal Letters. The study was led by Anastasia Fialkov, a postdoc researcher and Fellow at the CfA’s Institute for Theory and Computation (ITC). She was joined by Professor Abraham Loeb, the director of the ITC and the Frank B. Baird, Jr. Professor of Science at Harvard.

As noted, FRBs have remained something of a mystery since they were first discovered. Not only do their causes remain unknown, but much about their true is still not understood. As Dr. Fialkov told Universe Today via email:

“FRBs (or fast radio bursts) are astrophysical signals of an undetermined nature. The observed bursts are short (or millisecond duration), bright pulses in the radio part of the electromagnetic spectrum (at GHz frequencies). Only 24 bursts have been observed so far and we still do not know for sure which physical processes trigger them. The most plausible explanation is that they are launched by rotating magnetized neutron stars. However, this theory is to be confirmed.”

For the sake of their study, Fialkov and Loeb relied on observations made by multiple telescopes of the repeating fast radio burst known as FRB 121102. This FRB was first observed in 2012 by researchers using the Arecibo radio telescope in Puerto Rico, and has since been confirmed to be coming from a galaxy located 3 billion light years away in the direction of the Auriga constellation.

Since it was discovered, additional bursts have been detected coming from its location, making FRB 121102 the only known example of a repeating FRB. This repetitive nature has also allowed astronomers to conduct more detailed studies of it than any other FRB. As Prof. Loeb told Universe Today via email, these and other reasons made it an ideal target for their study:

“FRB 121102 is the only FRB for which a host galaxy and a distance were identified. It is also the only repeating FRB source from which we detected hundreds of FRBs by now. The radio spectrum of its FRBs is centered on a characteristic frequency and not covering a very broad band. This has important implications for the detectability of such FRBs, because in order to find them the radio observatory needs to be tuned to their frequency.”

Image of the sky where the radio burst FRB 121102 was found, in the constellation Auriga. You can see its location with a green circle. At left is supernova remnant S147 and at right, a star formation area called IC 410. Credit: Rogelio Bernal Andreo (DeepSkyColors.com)

Based on what is known about FRB 121102, Fialkov and Loeb conducted a series of calculations that assumed that it’s behavior was representative of all FRBs. They then projected how many FRBs would exist across the entire sky and determined that within the observable Universe, a FRB would likely be taking place once every second. As Dr. Fialkov explained:

“Assuming that FRBs are produced by galaxies of a particular type (e.g., similar to FRB 121102) we can calculate how many FRBs have to be produced by each galaxy to explain the existing observations (i.e., 2000 per sky per day). With this number in mind we can infer the production rate for the entire population of galaxies. This calculation shows that an FRB occurs every second when accounting for all the faint events.”

While the exact nature and origins of FRBs are still unknown – suggestions include rotating neutron stars and even alien intelligence! – Fialkov and Loeb indicate that they could be used to study the structure and evolution of the Universe. If indeed they occur with such regular frequency throughout the cosmos, then more distant sources could act as probes which astronomers would then rely on to plumb the depths of space.

For instance, over vast cosmic distances, there is a significant amount of intervening material that makes it difficult for astronomers to study the Cosmic Microwave Background (CMB) – the leftover radiation from the Big Bang. Studies of this intervening material could lead to a new estimates of just how dense space is – i.e. how much of it is composed of ordinary matter, dark matter, and dark energy – and how rapidly it is expanding.

Gemini composite image of the field around FRB 121102, the only repeating FRB discovered so far. Credit: Gemini Observatory/AURA/NSF/NRC

And as Prof. Loeb indicated, FRBs could also be used to explore enduring cosmlogical questions, like how the “Dark Age” of the Universe ended:

“FRBs can be used to measure the column of free electrons towards their source. This can be used to measure the density of ordinary matter between galaxies in the present-day universe. In addition, FRBs at early cosmic times can be used to find out when the ultraviolet light from the first stars broke up the primordial atoms of hydrogen left over from the Big Bang into their constituent electrons and protons.”

The “Dark Age”, which occurred between 380,000 and 150 million years after the Big Bang, was characterized by a “fog” of hydrogen atoms interacting with photons. As a result of this, the radiation of this period is undetectable by our current instruments. At present, scientists are still attempting to resolve how the Universe made the transition between these “Dark Ages” and subsequent epochs when the Universe was filled with light.

This period of “reionization”, which took place 150 million to 1 billion years after the Big Bang, was when the first stars and quasars formed. It is generally believed that UV light from the first stars in the Universe traveled outwards to ionize the hydrogen gas (thus clearing the fog). A recent study also suggested that black holes that existed in the early Universe created the necessary “winds” that allowed this ionizing radiation to escape.

To this end, FRBs could be used to probe into this early period of the Universe and determine what broke down this “fog” and allowed light to escape. Studying very distant FRBs could allow scientists to study where, when and how this process of “reionization” occurred. Looking ahead, Fialkov and Loeb explained how future radio telescopes will be able to discover many FRBs.

The planned Square Kilometer Array will be the world’s largest radio telescope when it begins operations in 2018. Credit: SKA

“Future radio observatories, like the Square Kilometer Array, will be sensitive enough to detect FRBs from the first generation of galaxies at the edge of the observable universe,” said Prof. Loeb. “Our work provides the first estimate of the number and properties of the first flashes of radio waves that lit up in the infant universe.”

And then there’s the Canadian Hydrogen Intensity Mapping Experiment (CHIME) at the at the Dominion Radio Astrophysical Observatory in British Columbia, which recently began operating. These and other instruments will serve as powerful tools for detecting FRBs, which in turn could be used to view previously unseen regions of time and space, and unlock some of the deepest cosmological mysteries.

“[W]e find that a next generation telescope (with a much better sensitivity than the existing ones) is expected to see many more FRBs than what is observed today,” said Dr. Fialkov. “This would allow to characterize the population of FRBs and identify their origin. Understanding the nature of FRBs will be a major breakthrough. Once the properties of these sources are known, FRBs can be used as cosmic beacons to explore the Universe. One application is to study the history of reionization (cosmic phase transition when the inter-galactic gas was ionized by stars).”

It is an inspired thought, using natural cosmic phenomena as research tools. In that respect, using FRBs to probe the most distant objects in space (and as far back in time as we can) is kind of like using quasars as navigational beacons. In the end, advancing our knowledge of the Universe allows us to explore more of it.

Further Reading: CfA, Astrophysical Journal Letters

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More Surface Ice on Mercury than Previously Thought, says New Study

September 20th, 2017

Back in 2012, scientists were delighted to discover that within the polar regions of Mercury, vast amounts of water ice were detected. While the existence of water ice in this permanently-shaded region had been the subject of speculation for about 20 years, it was only after the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft studied the polar region that this was confirmed.

Based on the MESSENGER data, it was estimated that Mercury could have between 100 billion to 1 trillion tons of water ice at both poles, and that the ice could be up to 20 meters (65.5 ft) deep in places. However, a new study by a team of researchers from Brown University indicates that there could be three additional large craters and many more smaller ones in the northern polar region that also contain ice.

The study, titled “New Evidence for Surface Water Ice in Small-Scale Cold Traps and in Three Large Craters at the North Polar Region of Mercury from the Mercury Laser Altimeter“, was recently published in the Geophysical Research Letters. Led by Ariel Deutsch, a NASA ASTAR Fellow and a PhD candidate at Brown University, the team considered how small-scale deposits could dramatically increase the overall amount of ice on Mercury.

Artist’s concept of the MESSENGER spacecraft on approach to Mercury. Credit: NASA/JPL

Despite being the closest planet to the Sun, and experiencing scorching surface temperatures on its Sun-facing side, Mercury’s low axial tilt means that its polar regions are permanently shaded and experience average temperatures of about 200 K (-73 °C; -100 °F). The idea that ice might exist in these regions dates back to the 1990s, when Earth-based radar telescopes detected highly reflective spots within the polar craters.

This was confirmed when the MESSENGER spacecraft detected neutron signals from the planet’s north pole that were consistent with water ice. Since that time, it has been the general consensus that Mercury’s surface ice was confined to seven large craters. But as Ariel Deutsch explained in a Brown University press statement, she and her team sought to look beyond them:

“The assumption has been that surface ice on Mercury exists predominantly in large craters, but we show evidence for these smaller-scale deposits as well. Adding these small-scale deposits to the large deposits within craters adds significantly to the surface ice inventory on Mercury.”

For the sake of this new study, Deutsch was joined by Gregory A. Neumann, a research scientist from NASA’s Goddard Space Flight Center, and James W. Head. In addition to being a professor the Department of Earth, Environmental and Planetary Sciences at Brown, Head was also a co-investigator for the MESSENGER and the Lunar Reconnaissance Orbiter missions.

A view of the crater Prokofiev on Mercury. The crater is the largest one on the planet’s north pole area to have “radar-bright” material, a probable sign of ice. Credit: NASA/JHUAPL/CIW

Together, they examined data from MESSENGER’s Mercury Laser Altimeter (MLA) instrument. This instrument was used by MESSENGER to measure the distance between the spacecraft and Mercury, the resulting data being then used to create detailed topographical maps of the planet’s surface. But in this case, the MLA was used to measure surface reflectance, which indicated the presence of ice.

As an instrument specialist with the MESSENGER mission, Neumann was responsible for calibrating the altimeter’s reflectance signal. These signals can vary based on whether the measurements are taken from overhead or at an angle (the latter of which is refereed to as “off-nadir” readings). Thanks to Neumann’s adjustments, researchers were able to detect high-reflectance deposits in three more large craters that were consistent with water ice.

According to their estimates, these three craters could contain ice sheets that measure about 3,400 square kilometers (1313 mi²). In addition, the team also looked at the terrain surrounding these three large craters. While these areas were not as reflective as the ice sheets inside the craters, they were brighter than the Mercury’s average surface reflectance.

Beyond this, they also looked at altimeter data to seek out evidence of smaller scale deposits. What they found was four smaller craters, each with diameters of less than 5 km (3 mi), which were also more reflective than the surface. From this, they deduced that there were not only more large deposits of ice that were previously undiscovered, but likely many smaller “cold traps” where ice could exist as well.

A forced perspective view of Mercury’s cratered north pole, showing the presence of water ice in yellow. Credit: NASA/JHUAPL/CIW

Between these three newly-discovered large deposits, and what could be hundreds of smaller deposits, the total volume of ice on Mercury could be considerably more than we previously thought. As Deutsch said:

“We suggest that this enhanced reflectance signature is driven by small-scale patches of ice that are spread throughout this terrain. Most of these patches are too small to resolve individually with the altimeter instrument, but collectively they contribute to the overall enhanced reflectance… These four were just the ones we could resolve with the MESSENGER instruments. We think there are probably many, many more of these, ranging in sizes from a kilometer down to a few centimeters.”

In the past, studies of the lunar surface also confirmed the presence of water ice in its cratered polar regions. Further research indicated that outside of the larger craters, small “cold traps”could also contain ice. According to some models, accounting for these smaller deposits could effectively double estimates on the total amounts of ice on the Moon. Much the same could be true for Mercury.

But as Jim Head (who also served as Deutsch Ph.D. advisor for this study) indicated, this work also adds a new take to the critical question of where water in the Solar System came from. “One of the major things we want to understand is how water and other volatiles are distributed through the inner Solar System—including Earth, the Moon and our planetary neighbors,” he said. “This study opens our eyes to new places to look for evidence of water, and suggests there’s a whole lot more of it on Mercury than we thought.”

This shaded relief image shows the Moon’s Shackleton Crater, a 21-km-wide crater permanently shadowed crater near the lunar south pole. The crater’s interior structure is shown in false color based on data from NASA’s LRO probe. Credit: NASA

In addition to indicating the Solar System may be more watery than previously suspected, the presence of abundant ice on Mercury and the Moon has bolstered proposals for building outposts on these bodies. These outposts could be capable of turning local deposits water ice into hydrazine fuel, which would drastically reduce the costs of mounting long-range missions throughout the Solar System.

On the less-speculative side of things, this study also offers new insights into how the Solar System formed and evolved. If water is far more plentiful today than we knew, it would indicate that more was present during the early epochs of planetary formation, presumably when it was being distributed throughout the Solar System by asteroids and comets.

Further Reading: Brown University, Geophysical Research Letters

The post More Surface Ice on Mercury than Previously Thought, says New Study appeared first on Universe Today.



Weekly Space Hangout -Sept 20, 2017: ANU Citizen Science Project for Supernovae

September 20th, 2017

Hosts:
Fraser Cain (universetoday.com / @fcain)
Dr. Paul M. Sutter (pmsutter.com / @PaulMattSutter)
Dr. Kimberly Cartier ( KimberlyCartier.org / @AstroKimCartier )
Dr. Morgan Rehnberg (MorganRehnberg.com / @MorganRehnberg ChartYourWorld.org)

Special Guest:
This week’s guests are Dr Brad Tucker (@btucker22) and Dr Anais Möller (@anais_moller) of ANU Citizen Science Project for Supernovae. Brad is an Astrophysicist/Cosmologist, and currently a Research Fellow at the Research School of Astronomy and Astrophysics, Mt. Stromlo Observatory at the Australian National University. Anais is a cosmologist based in the Australian National University with an expertise in type Ia supernova cosmology. She has worked at low and high redshift supernovae surveys with the goal to study the effect of dark energy in our Universe.

Announcements:

If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!

We record the Weekly Space Hangout every Friday at 5:00 pm Pacific / 8:00 pm Eastern. You can watch us live on Universe Today, or the Weekly Space Hangout YouTube page

The post Weekly Space Hangout -Sept 20, 2017: ANU Citizen Science Project for Supernovae appeared first on Universe Today.



300 Asteroids to be Explored by a Fleet of Nanosatellites

September 20th, 2017

The more that planetary astronomers study asteroids, they more they’re realizing just how varied and different they can be. Some, like 16 Psyche are made of solid nickel and iron, while others are made of rock. Some asteroids have been found with moons, rings, and some icy objects really blur the line between comet and asteroid. In order to truly understand their nature, it would take dozens or maybe hundreds of individual missions on the scale of Rosetta or New Horizons.

Or maybe not.

Asteroid 1998 QE2 and its moon

Asteroid 1998 QE2 and its moon


A team of researchers with the Finnish Meteorological Institute announced today that the best way to explore the varied objects in the asteroid belt would be with a fleet of tiny nanosatellites – 50 ought to do the trick to explore 300 separate asteroids, bringing the individual costs down to a few hundred thousand dollars per asteroid. During a presentation they made at the European Planetary Science Congress (EPSC) 2017 in Riga on Tuesday, the researchers showed how these tiny satellites could travel out to the asteroid belt, gather data on individual asteroids, and return to Earth to download their data.

The 50 satellites could be launched together in a single vehicle, and then separate once in space, or they could fill extra space in existing launches. The exact launch orbit doesn’t matter, as long as the spacecraft can get outside the Earth’s protective magnetosphere, where they can catch a ride on the solar wind.

Once in space, 5-kg spacecraft would deploy a 20 km-long wire tether that would catch the solar wind; the constantly flowing particles coming off the Sun, imparting a tiny thrust. This is known as an “E-sail” or electric sail. Unlike a solar sail, which depends on the momentum of photons coming from the Sun, electric sails harvest the momentum of charged protons.

Artist's illustration of the Heliopause Electrostatic Rapid Transit System.

Artist’s illustration of the Heliopause Electrostatic Rapid Transit System.

Researchers are still figuring out if this is an effective propulsion system for spacecraft. An Estonian prototype satellite was launched back in 2015, but its onboard motor failed to reel out its tether. The Finnish Aalto-1 satellite launched in June, 2017, and will test out a prototype electric sail in addition to several other experiments over the course of the next year. Even more advanced versions have been proposed, such as Heliopause Electrostatic Rapid Transit System (or HERTS), a mission which could reach 100 astronomical units in 10-15 years by deploying a huge electrified net in space.

In the case of this asteroid mission, each satellite’s electric sail would only give it a change in velocity of only one millimeter per second, but over the course of a 3.2 year mission, it would allow the spacecraft to reach the asteroid belt and return to Earth.

Mission trajectory. The spacecraft would take 3.2 years to reach the asteroid belt and return.

Mission trajectory. The spacecraft would take 3.2 years to reach the asteroid belt and return.

In fact, the spacecraft would use their tethers to maneuver within the asteroid belt, flying past as many targets as they can with this minuscule thrust. Each satellite should be able to reach at least 6-7 numbers asteroids, and maybe even more smaller ones.

Each satellite would be equipped with a telescope with only a 40 mm aperture. That’s the size of a small spotting scope or half a pair of binoculars, but it would be enough to resolve features on the surface of an asteroid as large as 100 meters across from 1,000 km away. In addition to taking visual images of the asteroid targets, the spacecraft would be equipped with an infrared spectrometer to determine its meteorology.

Because the spacecraft are so small, they won’t be capable of carrying a transmitter to send their data back to Earth. Instead, they’d store all their scientific findings on a memory card, and then dump their data when their orbit brings them back close to Earth.

The researchers estimate that development of the mission would probably cost about 60 million Euros, or $70 million dollars, bringing the cost per asteroid down to about 200,000 Euros or $240,000.

Further Reading: Europlanet, Science Daily

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New Study Says Primordial Asteroid Belt was Empty

September 20th, 2017

Between the orbits of Mars and Jupiter lies a disk of rocks, small bodies and planetoids known as the Main Asteroid Belt. The existence of this Belt was first theorized in the 18th century, based on observations that indicated a regular pattern in the orbits of Solar planets. By the following century, regular discoveries began to be made in the space between Mars and Jupiter, prompting astronomers to theorize where the Belt came from.

For a long time, scientists debated whether the Belt was the remains of a planet that broke up, or remnants left over from the early system that failed to become a planet. But a new study by a pair of astronomers from the University of Bordeaux has offered a different take. According to their theory, the Asteroid Belt began as an empty space which was gradually filled by rocks and debris over time.

For the sake of their study – which recently appeared in the journal Science Advances under the title “The Empty Primordial Asteroid Belt” – astronomers Sean N. Raymond and Andre Izidoro of the University of Bordeaux considered the current scientific consensus, which is that the Main Belt was once much more densely packed and became depleted of mass over time.

Artist’s impression of how the Asteroid Belt could have become filled with C-type and S-type asteroids over time. Credit: Sean Raymond/planetplanet.net

As Dr. Raymond explained to Universe Today via email:

“The standard picture is that the building blocks of the Solar System — what we call planetesimals, generally thought of as 10-100 km-scale bodies — started off in a smooth distribution across the Sun’s planet-forming disk. The problem is, that puts a couple of times Earth’s mass in the asteroid belt, where there is now less than a thousandth of an Earth mass. The challenge in this picture is therefore to understand how the belt lost 99.9% of its mass (but not 100%).”

To this, Dr. Raymond and Dr. Izodoro considered the alternate possibility that perhaps the primordial belt started as an empty space. In accordance with this theory, there were no planetesimals – i.e. Ceres, Vesta, Palla, and Hygeia – orbiting between Mars and Jupiter as there are today. This began as a thought experiment which, as Dr. Raymond admits, sounded a bit crazy at first.

However, he and Dr. Izodoro soon realized that several protoplanetary disks like the one they were envisioning had already been discovered in other star systems. For example, in 2014, the Atacama Large Millimeter/submillimeter Array in Chile photographed a planet-forming disk of dust and gas (aka, a protoplanetary disk) in the HL Tauri system, a very young star located about 450 light years away in the Taurus constellation.

As the image (shown below) revealed, the dust in this disk is not smooth, but consists of several broad regions and less dense regions. “The exact explanation for the structure in this disk is still debated but pretty much all models invoke drifting dust,” said Raymond. “And planetesimals form when drifting dust piles up into sufficiently-dense rings. So, dust rings should (we think) produce rings of planetesimals.”

Image of the HL Tau planet-forming disk taken with the Atacama Large Millimeter Array. Credit: ALMA (ESO/NAOJ/NRAO)

To test this hypothesis, they constructed a model of the early Solar System which included an empty Main Belt region. As they moved the simulation forward, they found that the formation of the disk was related to the formation of the rocky planets, and would gradually become what we see today. As Raymond indicated:

“What we found is that the growth of the rocky planets is not 100% efficient. A fraction of planetesimals is gravitationally kicked outward and stranded in the asteroid belt. The orbits of captured bodies matches closely those of S-type asteroids. The efficiency of implanting S-types in the belt is quite low, only about 1 in 1000.  However, recall that the belt is almost empty.  There is a total of about 4 hundred-thousandths of an Earth-mass in S-types in the present-day belt.  Our simulations typically implanted a few times that amount. Given that some are lost during later evolution of the Solar System, this matches both the distribution and amount of S-type asteroids in the belt.

They then combined this model with previous work which looked at the growth of Jupiter and Saturn and how this would effect the Solar System. In this study, they showed the C-type asteroids would be deposited in the Belt over time, and that these asteroids would also be responsible for delivering water to Earth. When they combined the distribution of implanted C-type and S-type asteroids with their current work, they found that it matched the present-day distribution of asteroids.

Interestingly enough, this is not the first theory Raymond and Izodoro have come up with to address the Asteroid Belt’s missing mass. Back in 2011, Raymond was a co-author on the study that proposed the Grand Tack model, in which he and his colleagues proposed that Jupiter migrated from its original orbit after it formed. At first, the planet moved closer to Mars’ current orbit, then back out towards where it is today.

Diagram comparing two possible explanations for how the Asteroid Belt formed. Credit: Sean Raymond/planetplanet.net

In the process, the asteroid belt would have been cleared, and Mars would have been deprived of mass, thus leading to its diminutive size – relative to Earth and Venus. This resolved a key problem with classical theories of Asteroid Belt formation, which was known as the “small Mars problem”. In short, all previous simulations of Solar planet formation tended to produce Mars analogs that were far more massive than Mars is today.

However, the Grand Tack hypothesis still contained theoretical uncertainties, which prompted Raymond and Izodoro to consider the the Empty Primordial Belt theory. “Our new result lends credence to an alternate model in which planetesimals never formed in the asteroid belt at all,” he said. “Different pieces of this new alternative model have been developed in recent years, and I think they add up to make a solid alternative to the Grand Tack model.”

Looking ahead, Raymond says that he and Izodoro hope to conduct further studies and simulations to see if either theory can be confirmed or falsified. “That’s the next step,” he said. “Until the next (seemingly-)crazy idea!”

Further Reading: Science Advances, PlanetPlanet

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Dawn Probe Finds Evidence of Subsurface Ice on Vesta

September 20th, 2017

In 2011, NASA’s Dawn spacecraft established orbit around the large asteroid (aka. planetoid) known as Vesta. Over the course of the next 14 months, the probe conducted detailed studies of Vesta’s surface with its suite of scientific instruments. These findings revealed much about the planetoid’s history, its surface features, and its structure – which is believed to be differentiated, like the rocky planets.

In addition, the probe collected vital information on Vesta’s ice content. After spending the past three years sifting through the probe’s data, a team of scientists has produced a new study that indicates the possibility of subsurface ice. These findings could have implications when it comes to our understanding of how Solar bodies formed and how water was historically transported throughout the Solar System.

Their study, titled “Orbital Bistatic Radar Observations of Asteroid Vesta by the Dawn Mission“, was recently published in the scientific journal Nature Communications. Led by Elizabeth Palmer, a graduate student from Western Michigan University, the team relied on data obtained by the communications antenna aboard the Dawn spacecraft to conduct the first orbital bistatic radar (BSR) observation of Vesta.

Artist rendition of Dawn spacecraft orbiting Vesta. Credit: NASA/JPL-Caltech

This antenna – the High-Gain telecommunications Antenna (HGA) – transmitted X-band radio waves during its orbit of Vesta to the Deep Space Network (DSN) antenna on Earth. During the majority of the mission, Dawn’s orbit was designed to ensure that the HGA was in the line of sight with ground stations on Earth. However, during occultations – when the probe passed behind Vesta for 5 to 33 minutes at a time – the probe was out of this line of sight.

Nevertheless, the antenna was continuously transmitting telemetry data, which caused the HGA-transmitted radar waves to be reflected off of Vesta’s surface. This technique, known as bistatic radar (BSR) observations has been used in the past to study the surfaces of terrestrial bodies like Mercury, Venus, the Moon, Mars, Saturn’s moon Titan, and the comet 67P/CG.

But as Palmer explained, using this technique to study a body like Vesta was a first for astronomers:

“This is the first time that a bistatic radar experiment was conducted in orbit around a small body, so this brought several unique challenges compared to the same experiment being done at large bodies like the Moon or Mars. For example, because the gravity field around Vesta is much weaker than Mars, the Dawn spacecraft does not have to orbit at a very high speed to maintain its distance from the surface. The orbital speed of the spacecraft becomes important, though, because the faster the orbit, the more the frequency of the ‘surface echo’ gets changed (Doppler shifted) compared to the frequency of the ‘direct signal’ (which is the unimpeded radio signal that travels directly from Dawn’s HGA to Earth’s Deep Space Network antennas without grazing Vesta’s surface). Researchers can tell the difference between a ‘surface echo’ and the ‘direct signal’ by their difference in frequency—so with Dawn’s slower orbital speed around Vesta, this frequency difference was very small, and required more time for us to process the BSR data and isolate the ‘surface echoes’ to measure their strength.”

This high-res geological map of Vesta is derived from Dawn spacecraft data. Brown colors represent the oldest, most heavily cratered surface. Credit: NASA/JPL-Caltech/ASU

By studying the reflected BSR waves, Palmer and her team were able to gain valuable information from Vesta’s surface. From this, they observed significant differences in surface radar reflectivity. But unlike the Moon, these variations in surface roughness could not be explained by cratering alone and was likely due to the existence of ground-ice. As Palmer explained:

“We found that this was the result of differences in the roughness of the surface at the scale of a few inches.  Stronger surface echoes indicate smoother surfaces, while weaker surface echoes have bounced off of rougher surfaces. When we compared our surface roughness map of Vesta with a map of subsurface hydrogen concentrations—which was measured by Dawn scientists using the Gamma Ray and Neutron Detector (GRaND) on the spacecraft—we found that extensive smoother areas overlapped areas that also had heightened hydrogen concentrations!”

In the end, Palmer and her colleagues concluded that the presence of buried ice (past and/or present) on Vesta was responsible for parts of the surface being smoother than others. Basically, whenever an impact happened on the surface, it transferred a great deal of energy to the subsurface. If buried ice was present there, it would be melted by the impact event, flow to the surface along impact-generated fractures, and then freeze in place.

Much in the same way that moon’s like Europa, Ganymede and Titania experience surface renewal because of the way cryovolcanism causes liquid water to reach the surface (where it refreezes), the presence of subsurface ice would cause parts of Vesta’ surface to be smoothed out over time. This would ultimately lead to the kinds of uneven terrain that Palmer and her colleagues witnessed.

The planetoid Vesta, which was studied by the Dawn probe between July 2011 and September 2012. Credit: NASA

This theory is supported by the large concentrations of hydrogen that were detected over smoother terrains that measure hundreds of square kilometers. It is also consistent with geomorphological evidence obtained from the Dawn Framing Camera images, which showed signs of of transient water flow over Vesta’s surface. This study also contradicted some previously-held assumptions about Vesta.

As Palmer noted, this could also have implications as far as our understanding of the history and evolution of the Solar System is concerned:

Asteroid Vesta was expected to have depleted any water content long ago through global melting, differentiation, and extensive regolith gardening by impacts from smaller bodies. However, our findings support the idea that buried ice may have existed on Vesta, which is an exciting prospect since Vesta is a protoplanet that represents an early stage in the formation of a planet. The more we learn about where water-ice exists throughout the Solar System, the better we will understand how water was delivered to Earth, and how much was intrinsic to Earth’s interior during the early stages of its formation.”

This work was sponsored by NASA’s Planetary Geology and Geophysics program, a JPL-based effort that focuses on fostering the research of terrestrial-like planets and major satellites in the Solar System. The work was also conducted with the assistance of the USC’s Viterbi School of Engineering as part of an ongoing effort to improve radar and microwave imaging to locate subsurface sources of water on planets and other bodies.

Further Reading: USC, Nature Communications

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Northrop Grumman Acquires Orbital ATK for $9.2 Billion

September 20th, 2017

Orbital ATK Antares rocket stands erect, reflecting off the calm waters the night before a launch from NASA’s Wallops Flight Facility, VA, on Oct. 28, 2014. Credit: Ken Kremer/kenkremer.com

Aerospace giant Northrop Grumman will acquire Orbital ATK for approximately $9.2 billion, in a deal the companies announced Monday and they say will “expand capability” is largely “complementary” and involves “little overlap.”

Orbital ATK specializes in a wide variety of launch vehicles, satellites, missiles and munitions that Northrop believes will significantly enhance capabilities it lacks while offering Orbital significantly more technical and financial resources to grow sales and business opportunities.

Under the terms of the huge deal West Falls Church, Virginia based Northrop will dole out approximately $7.8 billion in cash to buy Dulles, Virginia based Orbital ATK and assume $1.4 billion in net debt. Orbital ATK shareholders will receive all-cash consideration of $134.50 per share, which is about a 20% premium above the stock’s price of $110 per share at the close of trading Friday, Sept. 15.

Rumors of the deal first appeared on Sunday.

Orbital Sciences Corporation Antares rocket and Cygnus spacecraft blasts off on July 13 2014 from Launch Pad 0A at NASA Wallops Flight Facility , VA, on the Orb-2 mission and loaded with over 3000 pounds of science experiments and supplies for the crew aboard the International Space Station. Credit: Ken Kremer – kenkremer.com

The final purchase is expected to take place around mid-2018, subject to approval by government regulators and Orbital ATK shareholders.

The Boards of Directors of both companies have already given unanimous approval to the mega buyout.

“Our two companies represent a very complementary fit,” Wes Bush, chief executive officer and president of Northrop Grumman said in a conference call on Monday, Sept. 18.

“We have very little overlap, and we fully expect our combined portfolios of leading technologies, along with our aligned and innovation-focused cultures, to yield significant value creation through revenue, cost and operational synergies, accelerating our profitable growth trajectory.”

Northrop indicated that Orbital ATK will operate as a separate fourth unit – at least initially – and that Orbital programs will benefit from the increased financial resources available from Northrup.

“Upon completion of the acquisition, Northrop Grumman plans to establish Orbital ATK as a new, fourth business sector to ensure a strong focus on operating performance and a smooth transition into Northrop Grumman.”

For his part Orbital ATK CEO David Thompson was very pleased with the buyout and future opportunities.

“The agreement reflects the tremendous value that Orbital ATK has created for our customers, our shareholders and our employees,” David Thompson, Orbital ATK president and chief executive officer said at the conference call.

“The combination will allow our team as a new business sector within Northrop Grumman to maintain strong operational performance on existing customer programs and to pursue new opportunities that require greater technical and financial resources than we currently possess.”

“Our collective customers should benefit from the expanded capabilities for innovation, increased speed of delivery and improved affordability of production resulting from the combination.”

“The combination of our companies and human capital will also significantly benefit our customers,” Bush elaborated. “Together, we can offer our customers enhanced mission capabilities and more competitive offerings in areas such as space, missiles and strategic deterrents.

“Our shareholders can expect revenue synergies from these new business opportunities.”

Northrop Grumman sales for 2017 amount to about $25 billion vs. about $4.5 billion for Orbital ATK
Orbital ATK itself is the product of a very recent merger in 2015 of Orbital Sciences and ATK.

The company employs over 13,000 people including over 4,200 scientists and engineers. It holds a heft backlog of contracts worth more than $15 billion.

Northrop Grumman employs over 68,000 people and is the fifth largest defense contractor.

“The agreement will also provide expanded career options for our employees as part of a larger, more diverse aerospace and defense company,” said Thompson.

It will also benefit stockholders.

“The transaction represents a truly compelling financial proposition for our shareholders, valuing the enterprise at about $9.2 billion and providing our investors with more than 120% total return over the 3-year period from the completion of the Orbital ATK merger in early 2015 to the expected closing in the first half of 2018.”

Orbital ATK Minotaur IV rocket streaks to orbit through low hanging clouds that instantly illuminate as the booster engines flames pass through. This first Minotaur launch from the Cape carried the ORS-5 satellite tracker to equatorial orbit for the U.S. Air Force at 2:04 a.m. EDT on August 26, 2017 from Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com

Orbital ATK launchers run the gamut from small to medium to large.

The rockets include the massive solid rocket boosters for NASA’s Space Launch System (SLS) heavy lift rocket under development, the Antares liquid fueled booster used to launch Cygnus cargo freighters to the International Space Station for NASA, the Minotaur family of medium class solid rocket launchers, as well as sounding rockets for a variety of low weight science missions.

The most recent Orbital ATK launch took place on Aug. 26 when a Minotaur 4 rocket (a retired Peacekeeper ICBM) lifted off from Cape Canaveral with a USAF surveillance satellite.

Orbital ATK also has a thriving satellite manufacturing business building NASA science, commercial, government and military satellites.

Northrop Grumman is the prime contractor for NASA’s James Webb Space Telescope and designed the optics and spacecraft bus under contract for NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

The 18-segment gold coated primary mirror of NASA’s James Webb Space Telescope is raised into vertical alignment in the largest clean room at the agency’s Goddard Space Flight Center in Greenbelt, Maryland, on Nov. 2, 2016. The secondary mirror mount booms are folded down into stowed for launch configuration. Credit: Ken Kremer/kenkremer.com

The purchase is also estimated to result in $150 million in annual cost savings by 2020.

“We believe that this combination represents a compelling value creation opportunity for the customers, shareholders and employees of both our companies,” stated Bush. “Through our combination, all of our stakeholders will benefit from expanded capabilities, accelerated innovation and greater competitiveness in critical global security domains.”

Watch for Ken’s continuing onsite NASA mission and launch reports direct from the Kennedy Space Center, and Cape Canaveral Air Force Station, Florida, and NASA Wallops Flight Facility, Va.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

The Orbital ATK Antares rocket, with the Cygnus OA-5 spacecraft onboard, is raised into the vertical position on launch Pad-0A for planned launch on Oct. 17, 2016, at NASA’s Wallops Flight Facility in Virginia. Credit: Ken Kremer/kenkremer

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Venus Express Probe Reveals the Planet’s Mysterious Night Side

September 19th, 2017

Venus’ atmosphere is as mysterious as it is dense and scorching. For generations, scientists have sought to study it using ground-based telescopes, orbital missions, and the occasional atmospheric probe. And in 2006, the ESA’s Venus Express mission became the first probe to conduct long-term observations of the planet’s atmosphere, which revealed much about its dynamics.

Using this data, a team of international scientists – led by researchers from the Japan Aerospace and Exploration Agency (JAXA) – recently conducted a study that characterized the wind and upper cloud patterns on the night side of Venus. In addition to being the first of its kind, this study also revealed that the atmosphere behaves differently on the night side, which was unexpected.

The study, titled “Stationary Waves and Slowly Moving Features in the Night Upper Clouds of Venus“, recently appeared in the scientific journal Nature Astronomy. Led by Javier Peralta, the International Top Young Fellow of JAXA, the team consulted data obtained by Venus Express’ suite of scientific instruments in order to study the planet’s previously-unseen cloud types, morphologies, and dynamics.

The atmospheric super-rotation at the upper clouds of Venus. While the super-rotation is present in both day and night sides of Venus, it seems more uniform in the day. Credits: JAXA, ESA, J. Peralta and R. Hueso.

Whereas plenty of studies have been conducted of Venus’ atmosphere from soace, this was the first time that a study was not focused on the dayside of the planet. As Dr. Peralta explained in an ESA press statement:

This is the first time we’ve been able to characterize how the atmosphere circulates on the night side of Venus on a global scale. While the atmospheric circulation on the planet’s dayside has been extensively explored, there was still much to discover about the night side. We found that the cloud patterns there are different to those on the dayside, and influenced by Venus’ topography.

Since the 1960s, astronomers have been aware that Venus’ atmosphere behaves much differently that those of other terrestrial planets. Whereas Earth and Mars have atmospheres that co-rotate at approximately the same speed as the planet, Venus’ atmosphere can reach speeds of more than 360 km/h (224 mph). So while the planet takes 243 days to rotate once on its axis, the atmosphere takes only 4 days.

This phenomena, known as “super-rotation”, essentially means that the atmosphere moves over 60 times faster than the planet itself. In addition, measurements in the past have shown that the fastest clouds are located at the upper cloud level, 65 to 72 km (40 to 45 mi) above the surface. Despite decades of study, atmospheric models have been unable to reproduce super-rotation, which indicated that some of the mechanics were unknown.

Artist’s impression of the atmosphere of Venus, showing its lightning storms and a volcano in the distance. Credit and ©: European Space Agency/J. Whatmore

As such, Peralta and his international team – which included researchers from the Universidad del País Vasco in Spain, the University of Tokyo, the Kyoto Sangyo University, the Center for Astronomy and Astrophysics (ZAA) at Berlin Technical University, and the Institute of Astrophysics and Space Planetology in Rome – chose to look at the unexplored side to see what they could find. As he described it:

“We focused on the night side because it had been poorly explored; we can see the upper clouds on the planet’s night side via their thermal emission, but it’s been difficult to observe them properly because the contrast in our infrared images was too low to pick up enough detail.”

This consisted of observing Venus’ night side clouds with the probe’s Visible and Infrared Thermal Imaging Spectrometer (VIRTIS). The instrument gathered hundreds of images simultaneously and different wavelengths, which the team then combined to improve the visibility of the clouds. This allowed the team to see them properly for the first time, and also revealed some unexpected things about Venus’ night side atmosphere.

What they saw was that atmospheric rotation appeared to be more chaotic on the night side than what has been observed in the past on the dayside. The upper clouds also formed different shapes and morphologies – i.e. large, wavy, patchy, irregular and filament-like patterns  – and were dominated by stationary waves, where two waves moving in opposite directions cancel each other out and create a static weather pattern.

Examples of new types of cloud morphology discovered on the night side of Venus thanks to Venus Express (ESA) and the infrared telescope IRTF (NASA). Credits: ESA/NASA/J. Peralta and R. Hueso.

The 3D properties of these stationary waves were also obtained by combining VIRTIS data with radio-science data from the Venus Radio Science experiment (VeRa). Naturally, the team was surprised to find these kinds of atmospheric behaviors since they were inconsistent with what has been routinely observed on the dayside. Moreover, they contradict the best models for explaining the dynamics of Venus’ atmosphere.

Known as Global Circulation Models (GCMs), these models predict that on Venus, super-rotation would occur in much the same way on both the dayside and the night side. What’s more, they noticed that stationary waves on the night side appeared to coincide with high-elevation features. As Agustin Sánchez-Lavega, a researcher from the University del País Vasco and a co-author on the paper, explained:

Stationary waves are probably what we’d call gravity waves–in other words, rising waves generated lower in Venus’ atmosphere that appear not to move with the planet’s rotation. These waves are concentrated over steep, mountainous areas of Venus; this suggests that the planet’s topography is affecting what happens way up above in the clouds.

This is not the first time that scientists have spotted a possible link between Venus’ topography and its atmospheric motion. Last year, a team of European astronomers produced a study that showed how weather patterns and rising waves on the dayside appeared to be directly connected to topographical features. These findings were based on UV images taken by the Venus Monitoring Camera (VMC) on board the Venus Express.

Schematic illustration of the proposed behaviour of gravity waves in the vicinity of mountainous terrain on Venus. Credit: ESA

Finding something similar happening on the night side was something of a surprise, until they realized they weren’t the only ones to spot them. As Peralta indicated:

It was an exciting moment when we realized that some of the cloud features in the VIRTIS images didn’t move along with the atmosphere. We had a long debate about whether the results were real–until we realised that another team, led by co-author Dr. Kouyama, had also independently discovered stationary clouds on the night side using NASA’s Infrared Telescope Facility (IRTF) in Hawaii! Our findings were confirmed when JAXA’s Akatsuki spacecraft was inserted into orbit around Venus and immediately spotted the biggest stationary wave ever observed in the Solar System on Venus’ dayside.

These findings also challenge existing models of stationary waves, which are expected to form from the interaction of surface wind and high-elevation surface features. However, previous measurements conducted by the Soviet-era Venera landers have indicated that surface winds might too weak for this to happen on Venus. In addition, the southern hemisphere, which the team observed for their study, is quite low in elevation.

And as Ricardo Hueso of the University of the Basque Country (and a co-author on the paper) indicated, they did not detect corresponding stationary waves in the lower cloud levels. “We expected to find these waves in the lower levels because we see them in the upper levels, and we thought that they rose up through the cloud from the surface,” he said. “It’s an unexpected result for sure, and we’ll all need to revisit our models of Venus to explore its meaning.”

Artist’s impression of Venus Express performing aerobreaking maneuvers in the planet’s atmosphere in June and July 2014. Credit: ESA–C. Carreau

From this information, it seems that topography and elevation are linked when it comes to Venus’ atmospheric behavior, but not consistently. So the standing waves observed on Venus’ night side may be the result of some other undetected mechanism at work. Alas, it seems that Venus’ atmosphere – in particular, the key aspect of super-rotation – still has some mysteries for us.

The study also demonstrated the effectiveness of combining data from multiple sources to get a more detailed picture of a planet’s dynamics. With further improvements in instrumentation and data-sharing (and perhaps another mission or two to the surface) we can expect to get a clearer picture of what is powering Venus’ atmospheric dynamics before long.

With a little luck, there may yet come a day when we can model the atmosphere of Venus and predict its weather patterns as accurately as we do those of Earth.

Further Reading: ESA, Nature Astronomy

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