Posted on by Jon Voisey

Trojans May Yet Rain Down

It would be an interesting survey to catalog the initial reactions readers have to “Trojans”. Do you think first of wooden horses, or do asteroids spring to mind? Given the context of this website, I’d hope it’s the latter. If so, you’re thinking along the right lines. But how much do you really know about astronomical Trojans?

While most frequently used to discuss the set of objects in Jupiter’s orbital path that lie 60º ahead and behind the planet, orbiting the L4 and L5 Lagrange points, the term can be expanded to include any family of objects orbiting these points of relative stability around any other object. While Jupiter’s Trojan family is known to include over 3,000 objects, other solar system objects have been discovered with families of their own. Even one of Saturn’s moons, Tethys, has objects in its Lagrange points (although in this case, the objects are full moons in their own right: Calypso and Telesto).

In the past decade Neptunian Trojans have been discovered. By the end of this summer, six have been confirmed. Yet despite this small sample, these objects have some unexpected properties and may outnumber the number of asteroids in the main belt by an order of magnitude. However, they aren’t permanent and a paper published in the July issue of the International Journal of Astrobiology suggests that these reservoirs may produce many of the short period comets we see and “contribute a significant fraction of the impact hazard to the Earth.”

The origin of short period comets is an unusual one. While the sources of near Earth asteroids and long period comets have been well established, short period comets parent locations have been harder to pin down. Many have orbits with aphelions in the outer solar system, well past Neptune. This led to the independent prediction of a source of bodies in the far reaches by Edgeworth (1943) and Kuiper (1951). Yet others have aphelions well within the solar system. While some of this could be attributed to loss of energy from close passes to planets, it did not sufficiently account for the full number and astronomers began searching for other sources.

In 2006, J. Horner and N. Evans demonstrated the potential for objects from the outer solar system to be captured by the Jovian planets. In that paper, Horner and Evans considered the longevity of the stability of such captures for Jupiter Trojans. The two found that these objects were stable for billions of years but could eventually leak out. This would provide a storing of potential comets to help account for some of the oddities.

However, the Jupiter population is dynamically “cold” and does not contain a large distribution of velocities that would lead to more rapid shedding. Similarly, Saturn’s Trojan family was not found to be excited and was estimated to have a half life of ~2.5 billion years. One of the oddities of the Neptunian Trojans is that those few discovered thus far have tended to have high inclinations. This indicates that this family may be more dynamically excited, or “hotter” than that of other families, leading to a faster rate of shedding. Even with this realization, the full picture may not yet be clear given that searches for Trojans concentrate on the ecliptic and would likely miss additional members at higher inclinations, thus biasing surveys towards lower inclinations.

To assess the dangers of this excited population, Horner teamed with Patryk Lykawka to simulate the Neptunian Trojan system. From it, they estimated the family had a half life of ~550 million years. Objects leaving this population would then undergo several possible fates. In many cases, they resembled the Centaur class of objects with low eccentricities and with perihelion near Jupiter and aphelion near Neptune. Others picked up energy from other gas giants and were ejected from the solar system, and yet others became short period comets with aphelions near Jupiter.

Given the ability for this the Neptunian Trojans to eject members frequently, the two examined how many of the of short period comets we see may be from these reservoirs. Given the unknown nature of how large these stores are, the authors estimated that they could contribute as little as 3%. But if the populations are as large as some estimates have indicated, they would be sufficient to supply the entire collection of short period comets. Undoubtedly, the truth lies somewhere in between, but should it lie towards the upper end, the Neptunian Trojans could supply us with a new comet every 100 years on average.

Posted on by Nancy Atkinson

Warm ‘Perrier’ Ocean Could be Powering Enceladus’ Geysers

Proposed 'Perrier' Ocean for Enceladus. Credit: NASA/JPL/Space Science Institute

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Bottled water companies take note: an exotic form of warm, bubbly mineral water could be what feeds the mysterious jets spraying from the south polar region of Saturn’s moon Enceladus. A new model of the sub-surface ocean explains how the small moon could be so cryo-volcanically active. The Cassini spacecraft has detected sodium and potassium salts, as well as carbonates in the water vapor plumes spewing from the moon, which indicates a liquid, bubbly subsurface ocean. “There is a plume chamber, where some of the bubbles can pop the cap of the thin ice crust, and through that process is how the plumes get sprayed out,” said Dennis Matson, a NASA planetary scientist from JPL, speaking at a press briefing at the American Astronomical Society’s Division for Planetary Sciences meeting in Pasadena, California.

The schematic image (top) is laid on top of a picture of the Enceladus jets taken by Cassini’s imaging cameras in November 2009. It shows bubbles in subsurface seawater traveling through a passage in the ice crust to feed a geyser. The water flows back down to the subsurface ocean through cracks in the ice.

Matson explained the process:

“What we think is going on is that Enceladus has a subsurface ocean where water, heat and chemicals are stored before they erupt,” he said. There is an ice crust, many tens of kilometers thick. The ocean is gas rich, — and previous researchers dubbed such an ocean as a ‘Perrier’ ocean -– which basically “pops the cap” of the ice crust.

“What is happening is that water comes up and pressure is released,” said Matson. “Gases and water come out and the bubbles come near the surface and supply materials to the plumes. Water also transfers laterally, to a great extent, from the point of the plumes. This transfers heat to the surface, by analogy, like the radiator on your car. You have water coming out, which transfers heat to the thin ice layer, and then the heat is radiated to space. Cooled water goes down through cracks in the ice where it gets ready for another trip to the surface. “

This image compares heat flow at Earth and Saturn’s moon Enceladus. Credit: NASA/JPL

Cassini also found an impressive amount of heat flow over a small area coming from Enceladus’ interior. About four years ago, Cassini’s composite infrared spectrometer instrument detected a heat flow in the south polar region of at least 6 gigawatts, the equivalent of at least a dozen electric power plants. This is at least three times as much heat as an average region of Earth of similar area would produce, despite Enceladus’ small size.

“To put the heat flow in perspective,” said Matson, “the heat flow for the Earth has 87 of these units, but on the south pole of Enceladus, 250 units. At Yellowstone, there are 2500 units, but at one of the tiger stripe hots spots on Enceladus, we find heat flow as big as 13,000 units.”

The heat is, of course, relative to the surrounding environment. The subsurface bubbly water is probably just below freezing, which is 273 degrees Kelvin or 32 degrees Farenheit, whereas the surface is a frigid 80 degrees Kelvin or -316 degrees Farenheit. However, Matson said they have also seen surface temperatures as high as 180 K, when only 70 K was expected at the south pole.

Cassini imaging scientists used views like this one to help them identify the source locations for individual jets spurting ice particles, water vapor and trace organic compounds from the surface of Saturn's moon Enceladus. Credit: NASA

Finding the sodium in the icy grains in the plume is huge piece of evidence pointing to a subsurface ocean. Previously, Earth-based observations did not detect salts in the plume, and so scientists didn’t think a liquid ocean was possible. But infrared observations with an instrument on Cassini found the particles in the plumes include water ice, and substantial amounts of sodium and potassium salts and carbonates, as well as organics.

“The sodium was hiding in the little grains,” Matson said. “In the case of Enceladus, sodium isn’t in the vapor, it’s in the solid particles. This was something entirely new that had not been seen elsewhere.”

Also new is that the heat from Enceladus appears to be originating in the ocean, and also the realization there is a circulation system inside the moon, where there is process of pumping the water to the surface.

“This process we’ve outlined, where getting the water up to the surface, you have the heat, the water, and sodium and potassium all from one source that brings that up to the surface. So you have one process that delivers all those things, whereas before we had separate processes to try and explain each of them.”

Source: DPS press briefing

Posted on by Jason Rhian

Dragon Ascendant: SpaceX Prepares for Second Falcon 9 Launch

The business end of the Falcon 9 is shown in this image. These nine Merlin engines are scheduled to power the Falcon 9 to orbit this November. Photo Credit: SpaceX

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Earlier this year, SpaceX (Space Exploration Technologies) successfully launched the first of its Falcon 9 rockets. The firm has continued to move forward, prepping for the next demonstration flight. This mission will include the first flight of an operational Dragon spacecraft (the first payload was a spacecraft qualification unit), and will be the first demonstration launch under NASA’s Commercial Orbital Transportation Services (COTS)program. THe launch is currently scheduled to take place in the Nov. 8-9 timeframe.

Under the contract SpaceX is required to fly 3 demonstration flights and 12 operational missions to the International Space Station (ISS), to resupply the orbiting outpost.

The Dragon spacecraft shown here has significant payload capabilities and has both unmanned and manned versions planned. Photo Credit: SpaceX/Michael Rooks

Falcon 9’s second flight will liftoff from Cape Canaveral Air Force Station and will closely match the first flight. However, on this mission the Dragon spacecraft will separate from the second stage of the rocket and test a number of crucial flight requirements. Some of these include, maneuvering, communications, navigation and reentry. The Dragon is designed to make touchdown on terra-firma but its initial landings will occur on water. These landings will be provided via its Draco thrusters – which may enable the craft to land within a few hundred yards of the desired target.

For its first demo flight, the Dragon will test out its systems as it conducts a number of orbits around the Earth. Afterward it will fire its thrusters and reenter the Earth’s atmosphere. The splashdown is planned to take place in the Pacific Ocean off the coast of Southern California. The entire mission is not expected to last more than four hours.

In this image the Dragon spacecraft is mounted on a test stand in the hangar at Cape Canaveral. Photo Credit: SpaceX/Brian Attiyeh

While the Dragon spacecraft does not have the space shuttle’s payload capabilities – it is designed to return payloads weighing up to 6,600 lbs. The shuttle is the only other craft that has such a large cargo return capability. The Russian Progress M1 spacecraft has a similar payload capacity but it is not currently designed to return to Earth (the Progress burns up in the atmosphere). This would be a huge leap forward for returning payloads (and hopefully, eventually people) from the ISS.

Under NASA’s new direction, it is hoped that by investing in commercial crew transports that competition will be created and thus lower the cost for access to space.

SpaceX recently conducted a successful wet dress rehearsal (WDR) that included rolling the rocket out to the launch pad, located at Cape Canaveral Air Force Station’s Launch Complex 40. It was then loaded with fuel and went through a complete launch sequence – right up until launch. It was then de-fueled and “safed.” The procedures of the wet test included specific procedures required for the inclusion of an operational Dragon spacecraft.

The Falcon 9 demo-2 on the launch pad during the full wet dress rehearsal, which includes everything prior to engine ignition. Photo Credit: SpaceX

Before the WDR, SpaceX completed the first integration of its Falcon 9 and an operational Dragon spacecraft. The Dragon will be integrated onto the Falcon 9 rocket horizontally within the hangar. This helps to eliminate the cost of constructing and maintaining a vertical mobile service tower. It also makes processing of the payload less complicated. After integration is complete the Falcon 9 with the Dragon spacecraft will be moved to SpaceX’s mobile transporter/erector and be moved out of the hangar to the launch pad and then it will be erected vertically. The next step will be to conduct a static firing which is scheduled to take place in the coming weeks.

The Dragon is designed to be similar to the Russian Soyuz/Progress spacecraft in that they can be used to launch both materials and astronauts into orbit. The spacecraft includes eighteen Draco engines, hypergolic fuel systems, avionics, power systems, software, guidance, navigation, the largest PICA-based heat shield yet to fly, and a dual-redundant deployment system for the spacecraft’s three recovery parachutes.

NASA astronauts Cady Coleman and Scott Kelly go over spacecraft cargo operations with some of SpaceX's engineers. Photo Credit: SpaceX

NASA astronauts have been trained in how to use the Dragon’s systems. Under both the COTS and Commercial Resupply Services (CRS) programs over a dozen astronauts from NASA, the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA) have been taught how to use the spacecraft’s controls. There has been a mutual exchange of information, as the astronauts learned about the spacecraft’s operating systems, SpaceX employees have been given insights about what it takes to live and work in space. This knowledge will eventually make its way into procedures and flight hardware.

Posted on by Nancy Atkinson

So, You Want to Build a Satellite?

A light-hearted look from the upcoming MAVEN (Mars Atmosphere and Volatile Evolution) mission to Mars of what it takes to create a satellite mission for NASA — even before you ever start building it. And the MAVEN folks should know — NASA has just given the mission a green light to continue the development of the mission, which will investigate the mystery of how Mars lost much of its atmosphere. The approval to proceed followed a review at NASA Headquarters of the detailed plans, instrument suite, budget, and risk factor analysis for the spacecraft. You can see how that all works, (presumably problem free) in this witty little video.
Continue reading “So, You Want to Build a Satellite?”

Posted on by Nancy Atkinson

Moon Balloon Has Mostly Successful Test Flight

ARCA successfully launches the first Romanian space rocket, via balloon. Credit: ARCA

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A Romanian team aiming to send a rocket to the Moon via balloon successfully launched a test flight of their Helen 2 rocket, sending the first Romanian-made rocket system to 40,000 meters above the Earth. The Aeronautics and Cosmonautics Romanian Association (ARCA) team is vying for the Google Lunar X PRIZE, and tested the balloon/rocket system (sometimes called a ‘rockoon’) which launched from a Romanian naval frigate from the Black Sea. While the balloon and rocket worked great, the parachute and recovery system failed. But the team met their main objectives and were ecstatic.

A Romanian naval officer celebrates with a member of the ARCA team after the rocket fired successfully. Credit: ARCA

ARCA has a simple, “green” design. For getting the Moon, a super-huge balloon will carry a system of three rockets to about 18 km (11 miles). Then the first two rocket stages will fire and boost the system into low Earth orbit, and use the final stage to boost it to the Moon. The lander, the European Lunar Explorer (ELE) resembles a knobby rubber ball that uses its own rocket engine to ensure a soft landing. They consider their system to be green, as the rocket engine operates exclusively with hydrogen peroxide

The Helen rocket is lifted into the air by the balloon. Credit: ARCA

The balloon ascent took 40 minutes, bringing the system to an altitude of 14,000 m, at times raising the system at 120 km/h. When it reached that altitude, the flight controllers on the naval ship lit the rocket engines for 30 seconds, bringing it to 40,000 meters. From flight data transmitted to the control centers of ARCA and the Romanian civil aviation authority (ROMATSA) the team was able to confirm the successful flight trajectory, which had an error of only 800 m from the center of their safe trajectory.

A payload on board the capsule took pictures from the top of the trajectory.

An image sent down from the capsule from about 40,000 meters. Credit: ARCA

But at the capsule’s reentry, the parachute did not open, and a ship sent to try and find the capsule in the water was not able to find and retrieve it. But the ARCA team said they didn’t look for it for very long, since most data were transmitted by radio telemetry and satellite and recovery isn’t an objective of the Google Lunar X Prize Competition.

However, they were able to complete the successful launch of the first Romanian space rocket, as well as their first flight of the Google Lunar X Prize Competition. They also verified their rocket stabilization system, and reached the highest altitude ever by an object designed and built entirely in Romania.

In November 2009, ARCA’s test flight hopes were dashed when the balloon’s lines became entangled during inflation and had to be cut, and the test curtailed.

Rockoons were tried and then abandoned by the US in the 1950s because they blew off course in windy conditions.

Watch a video animation of the test flight:

See more images of the test flight at ARCA’s Picasa page.

Source: ARCA

Posted on by Nancy Atkinson

Titan-ic Tsunami Causing Crack in Saturn’s C Ring

This graphic shows an angled view of a newly discovered “crack” in one of Saturn’s rings, known as the C ring. This view shows the 3-D quality of the puzzling crack associated with a wave-like feature that was discovered earlier by NASA’s Voyager 1 spacecraft. Image credit: NASA/JPL/Cornell

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Saturn’s rings have several gaps, most of which are caused by small moons shepherding ring debris into breaks in the rocky rings. But one gap may be caused by gravitational perturbations from Saturn’s largest moon, Titan, sending tsunami-like waves up to 3 kilometers (2 miles) high in the C ring. This causes one region of the ring to spin like a warped, uneven vinyl record on a turntable. A new model of this action explains why the gap was narrower than expected and also why is seems to disappear from time to time. “What looked like a 15-kilometer-wide gap actually was this gap with a vertical displacement of about 3 kilometers projected and seen almost edge on,” said Phillip Nicholson from Cornell University, speaking at a press briefing at the American Astronomical Society’s Division for Planetary Sciences meeting in Pasadena, California. “It’s a little like a tsunami propagating away from an earthquake fault.”

The Cassini spacecraft looks close at Saturn to frame a view encompassing the entire C ring. Image credit: NASA/JPL/SSI

The gap in the middle of the C ring has been known since Voyager 1 flew by Saturn in the 1980, and it appeared there was a 15 km-wide gap. But when Cassini arrived in 2004 and began observations, the gap was only 2 km (1.5 miles) and sometimes it wasn’t there at all.

Nicholson said only when they began to think in three dimensions were they able to solve the mystery of this gap. While most of Saturn’s rings are flat, in 2009, the angle of sunlight during Saturn’s spring equinox revealed there were lumps and bumps in the rings are as high as the Rocky Mountains.

The model Nicholson and colleagues created suggests the actual gap in the ring is about a half a kilometer wide, but part of the ring rises 3 km (2 miles) in the air up. The different angles the two spacecraft observed from made the gap look wider to Voyager than to Cassini.

“The whole pattern rotates around at the same rate as the satellite Titan orbits Saturn, once every 16 days,” said Nicholson said. Sometimes, the tsunami-like wave couldn’t be seen by the spacecraft, which accounts for how the gap seems to appear and disappear.

Nicholson said this model explains the C ring gap, “better than you have any right to expect,” but there could be three or four dynamical processes going on that explains the other gaps.

Nicholson and Cassini Deputy Project Scientist Linda Spilker said the same types of processes seen in Saturn’s rings could also explain what is seen in disks of debris around other stars, with the theory that there are gaps forming in the disks associated with the formation of planets.

New insights into the nature of Saturn’s rings are revealed in this panoramic mosaic of 15 images taken during the planet’s August 2009 equinox. Image credit: NASA/JPL/SSI

“Saturn provides a wonderful natural laboratory of how protoplanetary nebula may evolve,” said Spilker.

The Cassini scientists also noted how the Cassini mission has now moved past the “Equinox” mission and is now in another extension of the mission called the Solstice mission, which will keep the spacecraft going until 2017.

Spilker shared how as the end of the mission approaches, they might try some riskier moves, such as try flying between Saturn’s D ring or heading into Saturn’s into upper atmosphere to “study new things about planet itself, for the end of the mission.”

Source: DPS meeting webcast

Posted on by Nicholos Wethington

Rosetta Uncovers a Thick, Dusty Blanket on Lutetia

An image taken by the Rosetta spacecraft on its closest approach to 21-Lutetia in July. Recent analysis of the data shows a thick, dusty blanket coating the asteroid. Image Credit:ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

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If you think that asteroids are boring, unchanging rocks floating in space waiting only to crop up in bad science fiction films, think again. Images and data that are being returned from various asteroid flybys – such as those by the Rosetta spacecraft and Hayabusa sample return mission – show that asteroids are dynamic, changing miniature worlds unto themselves.

During the recent flyby of the asteroid 21-Lutetia in July, the ESA’s Rosetta spacecraft took an amazing amount of data. After combing through all of this data over the past few months, astronomers have calculated that the asteroid is covered in a 2000-foot (600 meter)-thick blanket of rocks and dust called regolith. This dust is not unlike the outer layer of the Earth’s Moon, consisting of pulverized material that has accumulated over billions of years.

Rosetta is on a course to meet up with the comet 67P/Churyumov-Gerasimenko in 2014, but the spacecraft is no stranger to asteroid visits – on September 6th, 2008, Rosetta made its closest approach of the asteroid 2867-Steins. During this brief visit, Rosetta came within 500 miles (800km) of the small, diamond-shaped asteroid. Among the discoveries made were a chain of impact craters that were likely caused by the collision with a meteoroid stream, or the impact with another small body.

It then approached 21-Lutetia on July 10th of 2010, monitoring the asteroid with 17 instruments on board the spacecraft.

Rosetta took a number of images of the flyby, as well as examining the asteroid with electromagnetic detectors that covered the gamut from the UV to radio waves. Here’s a short animation showing the flyby:

Dr. Rita Schulz from the ESA Research and Scientific Support Department in the Netherlands presented this new information about 21-Lutetia’s regolith today at the Division for Planetary Sciences meeting in Pasadena, CA. She said that the regolith on the asteroid has been determined to be about 2000 feet (600 meters) thick, and that it resembles the regolith on the Moon. Images from the flyby reveal landslides, boulders, ridges, and other kinds of different geologic (or asterologic?) features.

21-Lutetia was determined by the July flyby to have a large, bowl-shaped impact crater on its surface, as well as an abundance of smaller craters. The thick covering of dust “softens” the sharper edges of impact craters in many of the images taken. Whether or not most asteroids of this size are covered in a similar blanket of material remains to be seen.

Boulders can be seen in this close-up image of 21-Lutetia, as taken by Rosetta during the July flyby. Image Credit: mage credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

In understanding more about asteroids and comets, astronomers are better able to hone their model of how our Solar System formed. By studying the composition and frequency of impacts of various asteroids, they can improve their data of just how things have changed since the primordial Solar System.

You can bet your boulders that Rosetta isn’t the only spacecraft to be making multiple rendezvous missions with the smaller denizens of our Solar System. Close flybys, impacts and landings on asteroids and comets are becoming almost commonplace for spacecraft.

There’s the Deep Impact mission, which slammed a huge copper weight into the comet Tempel 1, and has since been renamed EPOXI and is set to approach the comet Hartley 2. The upcoming approach of Vesta and Ceres by the Dawn mission is very much anticipated, and of course the recent success of the Hayabusa asteroid explorer has been a terrific tale of just how much we stand to learn from the trail of small celestial cairns that lead into our past.

Source: ESA, DPS Press Release

Posted on by Nancy Atkinson

ISS Instrument Detects X-ray Nova

Comparison of all-sky images before and after Sept. 25 when the nova was found. Credit: JAXA

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An instrument on board the International Space Station has discovered an X-ray nova. The science team from the Monitor of All-sky X-ray Image (MAXI) instrument on the Exposed Facility of the Japanese Kibo reported a short-lived X-ray nova became visible in the constellation of Ophiuchus on September 25, 2010, and the MAXI team confirmed that it was an uncatalogued X-ray source. Astronomers say the outburst is likely to be from a binary system with a black hole. The nova was named “MAXI J1659-152, in honor of the MAXI instrument.

X-ray novas appear suddenly in the sky and dramatically increases in strength over a period of a few days and then decreases, with an overall lifetime of a few months. Sometimes, these elusive novas have an optical counterpart. Unlike a conventional nova, in which the compact component is a white dwarf, an X-ray nova may be caused by material falling onto a neutron star or a black hole.

ESA’s INTEGRAL gamma-ray observatory also detected hard X-ray emission from the same position, and NASA’s Swift Observatory also was alerted by the flare-up. Following the discovery, many other astronomical observatories around the world have made follow-up observations in X-ray, gamma-ray, visible, infrared, and radio wavelengths. This discovery was led by Prof. Hitoshi Nego, a member of the MAXI team.

Source: JAXA

Posted on by Nancy Atkinson

Acid Rain-Like Chemistry Could Occur in Europa’s Ice Crust

Europa, a moon of Jupiter, appears as a thick crescent in this enhanced-color image from NASA's Galileo spacecraft. Credit: NASA

A new look at how chemicals on Jupiter’s moon Europa may be reacting together could provide new insight to how chemical reactions could be occurring in the moon’s icy crust, despite frigid temperatures. Researchers have found that water and sulfur dioxide react together very quickly, even at temperatures hundreds of degrees below freezing. Because the reaction occurs without the aid of radiation, it could take place throughout Europa’s thick coating of ice. If this is occurring, it would revamp current thinking about the chemistry and geology of this moon and perhaps others.

Europa has temperatures around 86 to 130 Kelvin (minus 300 to minus 225 degrees Fahrenheit), and in those extremely cold conditions, most chemical reactions require an infusion of energy from radiation or light. On Europa, the energy comes from particles from Jupiter’s radiation belts. Because most of those particles penetrate just fractions of an inch into the surface, models of Europa’s chemistry typically stop there.

“When people talk about chemistry on Europa, they typically talk about reactions that are driven by radiation,” says Goddard scientist Reggie Hudson. “Once you get below Europa’s surface, it’s cold and solid, and you normally don’t expect things to happen very fast under those conditions,” said Reggie Hudson, from NASA Goddard’s Astrochemistry Laboratory.

“But with the chemistry we describe,” said Mark Loeffler, who is first author on the paper being published in Geophysical Research Letters, “you could have ice 10 or 100 meters [roughly 33 or 330 feet] thick, and if it has sulfur dioxide mixed in, you’re going to have a reaction.”

Spectroscopy shows there is sulfur in Europa’s ice, and astronomers believe it originates from the volcanoes of Jupiter’s moon Io, then becomes ionized and is transported to Europa, where it gets embedded in the ice. But originally, astronomers thought not much of a reaction could occur between water ice and the sulfur.

Loeffler and Hudson sprayed water vapor and sulfur dioxide gas onto quarter-sized mirrors in a high-vacuum chamber. Because the mirrors were kept at about 50 to 100 Kelvin (about minus 370 to minus 280 degrees Fahrenheit), the gases immediately condensed as ice. As the reaction proceeded, the researchers used infrared spectroscopy to watch the decrease in concentrations of water and sulfur dioxide and the increase in concentrations of positive and negative ions generated.

Even with the extremely cold temperatures, the molecules reacted quickly in their icy forms. “At 130 Kelvin [about minus 225 degrees Fahrenheit], which represents the warm end of the expected temperatures on Europa, this reaction is essentially instantaneous,” said Loeffler. “At 100 Kelvin, you can saturate the reaction after half a day to a day. If that doesn’t sound fast, remember that on geologic timescales-billions of years-a day is faster than the blink of an eye.”

To test the reaction, the researchers added frozen carbon dioxide, also known as dry ice, which is commonly found on icy bodies, including Europa. “If frozen carbon dioxide had blocked the reaction, we wouldn’t be nearly as interested,” said Hudson, “because then the reaction probably wouldn’t be relevant to Europa’s chemistry. It would be a laboratory curiosity.” But the reaction continued, which means it could be significant on Europa as well as Ganymede and Callisto, two more of Jupiter’s moons, and other places where both water and sulfur dioxide are present.

The reaction converted one-quarter to nearly one-third of the sulfur dioxide into different products. “This is an unexpectedly high yield for this chemical reaction,” said Loeffler. “We would have been happy with five percent.”

What’s more, the positive and negative ions produced will react with other molecules. This could lead to some intriguing chemistry, especially because bisulfite, a type of sulfur ion, and some other products of this reaction are refractory-stable enough to last for quite some time.

This new finding will certainly prompt new remote observations of Europa to see whether evidence of any reaction-based products can be found.

Source: JPL

Posted on by Nancy Atkinson

A Rainbow Across the Moon

A 'rainbow' appears on this image from the Lunar Reconnaissance Oribiter

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Even though it is not the mind-blowing experience of a double rainbow all the way across the sky, seeing a rainbow on the Moon is pretty unusual. This curious image from the Lunar Reconnaissance Orbiter shows a rainbow effect across 120 km of the lunar surface. And although water has recently been found on the Moon, water droplets have nothing to do with this rainbow. It comes from illumination conditions and viewing angles with having the Sun directly overhead of the LRO and the Moon.

“This image was acquired as the Sun was exactly overhead, allowing us to observe the ‘opposition surge,’said Brent Denevi, writing on the LRO Camera website. “This is a surge in brightness that occurs when the Sun is directly behind the observer because of two effects. First, there are no shadows seen on the surface, because each boulder and grain of soil’s shadow is hidden directly beneath it. Second, as the light reflects back to the observer it constructively interferes with itself.”

It is a very cool effect, giving the Moon a look having some unexpected color. Denevi said images that contain this type of effect are not just pretty, but useful, too. “They provide a huge new dataset for studying how light interacts with a particulate surface at different wavelengths,” he said. “Perhaps an esoteric-sounding field of study, but this data can help us understand the reflectance images and spectra we have of the Moon and other bodies throughout the Solar System.”

Read more on the LROC website.