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Thursday, April 13, 2017

An Astrobiologist's Dream: The Subsurface Oceans of Europa and Enceladus May Bear the Ingredients Necessary for Life...

An artist's concept of NASA's Cassini spacecraft flying through plumes of water vapor erupting from the surface of Saturn's moon Enceladus.
NASA / JPL - Caltech

NASA Missions Provide New Insights into 'Ocean Worlds' in Our Solar System (Press Release)

Two veteran NASA missions are providing new details about icy, ocean-bearing moons of Jupiter and Saturn, further heightening the scientific interest of these and other "ocean worlds" in our solar system and beyond. The findings are presented in papers published Thursday by researchers with NASA’s Cassini mission to Saturn and Hubble Space Telescope.

In the papers, Cassini scientists announce that a form of chemical energy that life can feed on appears to exist on Saturn's moon Enceladus, and Hubble researchers report additional evidence of plumes erupting from Jupiter's moon Europa.

“This is the closest we've come, so far, to identifying a place with some of the ingredients needed for a habitable environment,” said Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate at Headquarters in Washington. ”These results demonstrate the interconnected nature of NASA's science missions that are getting us closer to answering whether we are indeed alone or not.”

The paper from researchers with the Cassini mission, published in the journal Science, indicates hydrogen gas, which could potentially provide a chemical energy source for life, is pouring into the subsurface ocean of Enceladus from hydrothermal activity on the seafloor.

The presence of ample hydrogen in the moon's ocean means that microbes – if any exist there – could use it to obtain energy by combining the hydrogen with carbon dioxide dissolved in the water. This chemical reaction, known as "methanogenesis" because it produces methane as a byproduct, is at the root of the tree of life on Earth, and could even have been critical to the origin of life on our planet.

Life as we know it requires three primary ingredients: liquid water; a source of energy for metabolism; and the right chemical ingredients, primarily carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. With this finding, Cassini has shown that Enceladus – a small, icy moon a billion miles farther from the Sun than Earth – has nearly all of these ingredients for habitability. Cassini has not yet shown phosphorus and sulfur are present in the ocean, but scientists suspect them to be, since the rocky core of Enceladus is thought to be chemically similar to meteorites that contain the two elements.

"Confirmation that the chemical energy for life exists within the ocean of a small moon of Saturn is an important milestone in our search for habitable worlds beyond Earth," said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

The Cassini spacecraft detected the hydrogen in the plume of gas and icy material spraying from Enceladus during its last, and deepest, dive through the plume on Oct. 28, 2015. Cassini also sampled the plume's composition during flybys earlier in the mission. From these observations scientists have determined that nearly 98 percent of the gas in the plume is water, about 1 percent is hydrogen and the rest is a mixture of other molecules including carbon dioxide, methane and ammonia.

The measurement was made using Cassini's Ion and Neutral Mass Spectrometer (INMS) instrument, which sniffs gases to determine their composition. INMS was designed to sample the upper atmosphere of Saturn's moon Titan. After Cassini's surprising discovery of a towering plume of icy spray in 2005, emanating from hot cracks near the south pole, scientists turned its detectors toward the small moon.

Cassini wasn't designed to detect signs of life in the Enceladus plume – indeed, scientists didn't know the plume existed until after the spacecraft arrived at Saturn.

"Although we can't detect life, we've found that there's a food source there for it. It would be like a candy store for microbes," said Hunter Waite, lead author of the Cassini study.

The new findings are an independent line of evidence that hydrothermal activity is taking place in the Enceladus ocean. Previous results, published in March 2015, suggested hot water is interacting with rock beneath the sea; the new findings support that conclusion and add that the rock appears to be reacting chemically to produce the hydrogen.

The paper detailing new Hubble Space Telescope findings, published in The Astrophysical Journal Letters, reports on observations of Europa from 2016 in which a probable plume of material was seen erupting from the moon’s surface at the same location where Hubble saw evidence of a plume in 2014. These images bolster evidence that the Europa plumes could be a real phenomenon, flaring up intermittently in the same region on the moon's surface.

The newly imaged plume rises about 62 miles (100 kilometers) above Europa’s surface, while the one observed in 2014 was estimated to be about 30 miles (50 kilometers) high. Both correspond to the location of an unusually warm region that contains features that appear to be cracks in the moon’s icy crust, seen in the late 1990s by NASA's Galileo spacecraft. Researchers speculate that, like Enceladus, this could be evidence of water erupting from the moon’s interior.

“The plumes on Enceladus are associated with hotter regions, so after Hubble imaged this new plume-like feature on Europa, we looked at that location on the Galileo thermal map. We discovered that Europa’s plume candidate is sitting right on the thermal anomaly," said William Sparks of the Space Telescope Science Institute in Baltimore, Maryland. Sparks led the Hubble plume studies in both 2014 and 2016.

The researchers say if the plumes and the warm spot are linked, it could mean water being vented from beneath the moon's icy crust is warming the surrounding surface. Another idea is that water ejected by the plume falls onto the surface as a fine mist, changing the structure of the surface grains and allowing them to retain heat longer than the surrounding landscape.

For both the 2014 and 2016 observations, the team used Hubble's Space Telescope Imaging Spectrograph (STIS) to spot the plumes in ultraviolet light. As Europa passes in front of Jupiter, any atmospheric features around the edge of the moon block some of Jupiter’s light, allowing STIS to see the features in silhouette. Sparks and his team are continuing to use Hubble to monitor Europa for additional examples of plume candidates and hope to determine the frequency with which they appear.

NASA's future exploration of ocean worlds is enabled by Hubble's monitoring of Europa's putative plume activity and Cassini's long-term investigation of the Enceladus plume. In particular, both investigations are laying the groundwork for NASA's Europa Clipper mission, which is planned for launch in the 2020s.

“If there are plumes on Europa, as we now strongly suspect, with the Europa Clipper we will be ready for them,” said Jim Green, Director of Planetary Science, at NASA Headquarters.

Hubble's identification of a site which appears to have persistent, intermittent plume activity provides a tempting target for the Europa mission to investigate with its powerful suite of science instruments. In addition, some of Sparks' co-authors on the Hubble Europa studies are preparing a powerful ultraviolet camera to fly on Europa Clipper that will make similar measurements to Hubble's, but from thousands of times closer. And several members of the Cassini INMS team are developing an exquisitely sensitive, next-generation version of their instrument for flight on Europa Clipper.

An artist's concept of a plume of water vapor erupting from the surface of Europa, one of Jupiter's moons.
NASA / ESA / K. Retherford / SWRI

Tuesday, April 11, 2017

Photo and Video of the Day: Invasion of the Eagles!


Jess Peck

Check out this pic and YouTube video showing a dockworker feeding raw meat to a flock of bald eagles in Dutch Harbor, Alaska last summer. It's amazing that America's national bird is as common in The Last Frontier as coyotes are here in Los Angeles! Anyways, enjoy the video.

(Ignore the brief profanity at the beginning of this clip.)

Friday, April 07, 2017

Photos of the Day: Syria Becomes the Latest "Target" for U.S. Tomahawk Missiles...

A Tomahawk cruise missile is launched from a U.S. Navy destroyer out in the Mediterranean Sea to strike a Syrian military airfield...on April 6, 2017.
Department of Defense

Just thought I'd share these pics that were released by the Pentagon last night showing Tomahawk missiles being launched from U.S. warships to supposedly hit a Syrian airbase that was used to deploy aircraft that carried out a heinous chemical weapons attack on Syrian civilians three days ago. I say 'supposedly' because based on reports that I've read online (yes, I know that the key word here is 'online'), President Trump went out of his way to not cause any real damage to the al-Shayrat military airfield to prevent antagonizing Trump's good friend and puppet master in Moscow, Vladimir Putin. According to said reports, Putin wanted to help Trump get back on his feet after his approval rating dipped to historic levels by creating an event that would distract the media from continuing to focus on Trump's ties to Russia. (Word has it that Trump's rating dipped to 35% only after 74 days in office, whereas it took the rating of fellow GOP'er George W. Bush about 1,947 days to fall that low. Bill Clinton and Barack Obama's ratings have never sunk to that level...because Democrats!)


What better way to create a distraction than to have Bashar al-Assad, Syria's own leader and Putin's other puppet, stage a chemical attack on his own people at the behest of Putin that would force Trump to react? By giving a military response to such an atrocity, Trump would supposedly receive the sympathy of the same mainstream media that lambasted him for the last two or so years. And this is despite the fact that Trump wanted to avenge the "beautiful" Syrian babies that he tried through two failed Muslim bans to keep out of the United States. And I won't even delve into other reports mentioning that Trump has been secretly amassing U.S. ground forces inside Syria weeks before last night's missile strike.


Just how much more does Trump's approval rating need to drop for him to send our soldiers into battle on Syrian soil to fight anyone other than the Islamic State (who is the foe we should be focusing on) as a way to take our attention away from the fact that he's a terrible president doing Putin's bidding? I could type a lot more on this charade that Trump and Putin are trying to play, but I won't. Don't know if I should hope or dread that Trump will finally prove to the fools who voted for him that Trump's presidency poses as an existential threat not just to America but to the whole world in general... We shall see. Or hopefully we won't.

A Tomahawk cruise missile is launched from a U.S. Navy destroyer out in the Mediterranean Sea to strike a Syrian military airfield...on April 6, 2017.
Department of Defense

A Tomahawk cruise missile is launched from a U.S. Navy destroyer out in the Mediterranean Sea to strike a Syrian military airfield...on April 6, 2017.
Department of Defense

Thursday, April 06, 2017

Dawn Update: The Dwarf Planet It Orbits Has an Atmosphere...Sort of

Images of asteroid Vesta and dwarf planet Ceres...with hydrogen data (shaded in red) taken by NASA's Dawn spacecraft overlaid on both celestial bodies.
NASA / JPL - Caltech / UCLA / MPS / DLR / IDA / PSI

Ceres' Temporary Atmosphere Linked to Solar Activity (Press Release)

Scientists have long thought that Ceres may have a very weak, transient atmosphere, but mysteries lingered about its origin and why it's not always present. Now, researchers suggest that this temporary atmosphere appears to be related to the behavior of the Sun, rather than Ceres' proximity to the Sun. The study was conducted by scientists from NASA's Dawn mission and others who previously identified water vapor at Ceres using other observatories.

"We think the occurrence of Ceres' transient atmosphere is the product of solar activity," said Michaela Villarreal, lead author of the new study in the Astrophysical Journal Letters and researcher at the University of California, Los Angeles.

Ceres is the largest object in the asteroid belt that lies between Mars and Jupiter. When energetic particles from the Sun hit exposed ice and ice near the surface of the dwarf planet, it transfers energy to the water molecules as they collide. This frees the water molecules from the ground, allowing them to escape and create a tenuous atmosphere that may last for a week or so.

"Our results also have implications for other airless, water-rich bodies of the solar system, including the polar regions of the Moon and some asteroids," said Chris Russell, principal investigator of the Dawn mission, also at UCLA. "Atmospheric releases might be expected from their surfaces, too, when solar activity erupts." Before Dawn arrived in orbit at Ceres in 2015, evidence for an atmosphere had been detected by some observatories at certain times, but not others, suggesting that it is a transient phenomenon. In 1991, the International Ultraviolet Explorer satellite detected hydroxyl emission from Ceres, but not in 1990. Then, in 2007, the European Southern Observatory's Very Large Telescope searched for a hydroxide emission, but came up empty. The European Space Agency's Herschel Space Observatory detected water in the possible weak atmosphere, or "exosphere," of Ceres on three occasions, but did not on a fourth attempt.

As Dawn began its thorough study of Ceres in March 2015, scientists found ample evidence for water in the form of ice. The spacecraft's gamma ray and neutron detector (GRaND) has found that the uppermost surface is rich in hydrogen, which is consistent with broad expanses of water ice. This ice is nearer to the surface at higher latitudes, where temperatures are lower, a 2016 study published in the journal Science found. Ice has been detected directly at the small bright crater called Oxo and in at least one of the craters that are persistently in shadow in the northern hemisphere. Other research has suggested that persistently shadowed craters are likely to harbor ice. Additionally, the shapes of craters and other features are consistent with significant water-ice content in the crust.

Because of this evidence for abundant ice, many scientists think that Ceres' exosphere is created in a process similar to what occurs on comets, even though they are much smaller. In that model, the closer Ceres gets to the Sun, the more water vapor is released because of ice sublimating near or at the surface.

But the new study suggests comet-like behavior may not explain the mix of detections and non-detections of a weak atmosphere.

"Sublimation probably is present, but we don't think it's significant enough to produce the amount of exosphere that we're seeing," Villarreal said.

Villarreal and colleagues showed that past detections of the transient atmosphere coincided with higher concentrations of energetic protons from the Sun. Non-detections coincided with lower concentrations of these particles. What's more, the best detections of Ceres' atmosphere did not occur at its closest approach to the Sun. This suggests that solar activity, rather than Ceres' proximity to the Sun, is a more important factor in generating an exosphere.

The research began with a 2016 Science study led by Chris Russell. The study, using GRaND data, suggested that, during a six-day period in 2015, Ceres had accelerated electrons from the solar wind to very high energies.

In its orbital path, Ceres is currently getting closer to the Sun. But the Sun is now in a particularly quiet period, expected to last for several more years. Since their results indicate Ceres' exosphere is related to solar activity, study authors are predicting that the dwarf planet will have little to no atmosphere for some time. However, they recommend that other observatories monitor Ceres for future emissions.

Dawn is now in its extended mission and studying Ceres in a highly elliptical orbit. Engineers are maneuvering the spacecraft to a different orbital plane so that Ceres can be viewed in a new geometry. The primary science objective is to measure cosmic rays to help determine which chemical elements lie near the surface of Ceres. As a bonus, in late April, the Sun will be directly behind Dawn, when the spacecraft is at an altitude of about 12,300 miles (20,000 kilometers). Ceres will appear brighter than before in that configuration, and perhaps reveal more secrets about its composition and history.

The Dawn mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team.

Source: Jet Propulsion Laboratory

Tuesday, April 04, 2017

Cassini Update: A Little Over 5 Months Till The History-Making Spacecraft Meets Its Fate...

An artist's concept of NASA's Cassini spacecraft approaching the inner gap between Saturn and its rings...as Cassini begins the 'Grand Finale' of its 13-year-long mission at the ringed planet.
NASA / JPL -Caltech

NASA’s Cassini Mission Prepares for 'Grand Finale' at Saturn (Press Release)

NASA's Cassini spacecraft, in orbit around Saturn since 2004, is about to begin the final chapter of its remarkable story. On Wednesday, April 26, the spacecraft will make the first in a series of dives through the 1,500-mile-wide (2,400-kilometer) gap between Saturn and its rings as part of the mission’s grand finale.

"No spacecraft has ever gone through the unique region that we'll attempt to boldly cross 22 times," said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. "What we learn from Cassini’s daring final orbits will further our understanding of how giant planets, and planetary systems everywhere, form and evolve. This is truly discovery in action to the very end."

During its time at Saturn, Cassini has made numerous dramatic discoveries, including a global ocean that showed indications of hydrothermal activity within the icy moon Enceladus, and liquid methane seas on its moon Titan.

Now 20 years since launching from Earth, and after 13 years orbiting the ringed planet, Cassini is running low on fuel. In 2010, NASA decided to end the mission with a purposeful plunge into Saturn this year in order to protect and preserve the planet's moons for future exploration – especially the potentially habitable Enceladus.

But the beginning of the end for Cassini is, in many ways, like a whole new mission. Using expertise gained over the mission's many years, Cassini engineers designed a flight plan that will maximize the scientific value of sending the spacecraft toward its fateful plunge into the planet on Sept. 15. As it ticks off its terminal orbits during the next five months, the mission will rack up an impressive list of scientific achievements.

"This planned conclusion for Cassini's journey was far and away the preferred choice for the mission's scientists," said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. "Cassini will make some of its most extraordinary observations at the end of its long life."

The mission team hopes to gain powerful insights into the planet's internal structure and the origins of the rings, obtain the first-ever sampling of Saturn's atmosphere and particles coming from the main rings, and capture the closest-ever views of Saturn's clouds and inner rings. The team currently is making final checks on the list of commands the robotic probe will follow to carry out its science observations, called a sequence, as it begins the finale. That sequence is scheduled to be uploaded to the spacecraft on Tuesday, April 11.

Cassini will transition to its grand finale orbits, with a last close flyby of Saturn's giant moon Titan, on Saturday, April 22. As it has many times over the course of the mission, Titan's gravity will bend Cassini's flight path. Cassini's orbit then will shrink so that instead of making its closest approach to Saturn just outside the rings, it will begin passing between the planet and the inner edge of its rings.

"Based on our best models, we expect the gap to be clear of particles large enough to damage the spacecraft. But we're also being cautious by using our large antenna as a shield on the first pass, as we determine whether it's safe to expose the science instruments to that environment on future passes," said Earl Maize, Cassini project manager at JPL. "Certainly there are some unknowns, but that's one of the reasons we're doing this kind of daring exploration at the end of the mission."

In mid-September, following a distant encounter with Titan, the spacecraft's path will be bent so that it dives into the planet. When Cassini makes its final plunge into Saturn's atmosphere on Sept. 15, it will send data from several instruments – most notably, data on the atmosphere's composition – until its signal is lost.

"Cassini's grand finale is so much more than a final plunge," said Spilker. "It's a thrilling final chapter for our intrepid spacecraft, and so scientifically rich that it was the clear and obvious choice for how to end the mission."

Monday, April 03, 2017

New Horizons Update: Only 637 Days Till Its Flyby of 2014 MU69...

With the Milky Way in the backdrop, the predicted location of 2014 MU69 on January 1, 2019 is seen in this image taken by NASA's New Horizons spacecraft...on January 28, 2017.
NASA / JHUAPL / SWRI

New Horizons Halfway from Pluto to Next Flyby Target (News Release)

How time and our spacecraft fly – especially when you’re making history at 32,000 miles (51,500 kilometers) per hour.

Continuing on its path through the outer regions of the solar system, NASA’s New Horizons spacecraft has now traveled half the distance from Pluto – its storied first target – to 2014 MU69, the Kuiper Belt Object (KBO) it will fly past on Jan. 1, 2019. The spacecraft reached that milestone at midnight (UTC) on April 3 – or 8 p.m. ET on April 2 – when it was 486.19 million miles (782.45 million kilometers) beyond Pluto and the same distance from MU69.

“It’s fantastic to have completed half the journey to our next flyby; that flyby will set the record for the most distant world ever explored in the history of civilization,” said Alan Stern, New Horizons principal investigator from the Southwest Research Institute in Boulder, Colorado.

Later this week – at 21:24 UTC (or 5:24 p.m. ET) on April 7 – New Horizons will also reach the halfway point in time between closest approaches to Pluto, which occurred at 7:48 a.m. ET on July 14, 2015, and MU69, predicted for 2 a.m. ET on New Year’s Day 2019. The nearly five-day difference between the halfway markers of distance and time is due to the gravitational tug of the Sun. The spacecraft is actually getting slightly slower as it pulls away from the Sun’s gravity, so the spacecraft crosses the midpoint in distance a bit before it passes the midpoint in time.

Ready for a Rest

New Horizons will begin a new period of hibernation later this week. In fact, the spacecraft will be sleeping through the April 7 halfway timing marker to MU69, because mission operators at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, will have put the spacecraft into hibernation two hours beforehand.

The scheduled 157-day hibernation is well-deserved; New Horizons has been “awake” for almost two and a half years, since Dec. 6, 2014. Since then, in addition to its historic Pluto encounter and 16 subsequent months of relaying the data from that encounter back to Earth, New Horizons has made breakthrough, distant observations of a dozen Kuiper Belt Objects (KBOs), collected unique data on the dust and charged-particle environment of the Kuiper Belt, and studied the hydrogen gas that permeates the vast space surrounding the Sun, called the heliosphere.

“The January 2019 MU69 flyby is the next big event for us, but New Horizons is truly a mission to more broadly explore the Kuiper Belt,” said Hal Weaver, New Horizons project scientist from APL, in Laurel, Maryland. “In addition to MU69, we plan to study more than two-dozen other KBOs in the distance and measure the charged particle and dust environment all the way across the Kuiper Belt.”

New Horizons is currently 3.5 billion miles (5.7 billion kilometers) from Earth; at that distance, a radio signal sent from the operations team – and traveling at light speed – needs about five hours and 20 minutes to reach the spacecraft. All spacecraft systems are healthy and operating normally, and the spacecraft is on course for its MU69 flyby.

Source: NASA.Gov

****

An artist's concept of NASA's New Horizons spacecraft flying past 2014 MU69.
NASA / JHUAPL / SWRI / Steve Gribben

Saturday, April 01, 2017

Happy April Fool's Day!

Just thought I'd share this hilarious pic that I recently found on Twitter. Well... Hilarious if you're not a red baseball cap-wearing, MAGA-spewing troglodyte who voted for anyone in the Republican Party. This "logo" applies to the GOP as long as Donald Trump or at least his elk like Steve Bannon, Sean Spicer or Jeff Sessions are still in office. Until then, expect more illustrations like this that poke fun at America's Islamophobic, racist, environment-polluting, fanatically-Christian, xenophobic, universal healthcare-threatening, Russia-loving and Holocaust-denying regime to pop up on social media. Carry on!

FORGET THE ELEPHANT... This is the NEW logo for the Republican Party.

Friday, March 31, 2017

Photos of the Day: The Big Statue...

Posing with Shaquille O'Neal's new bronze statue at STAPLES Center in Los Angeles...on March 29, 2017.

Just thought I'd share these pics that I took at STAPLES Center in Los Angeles two days ago—when I visited the new bronze statue of 4-time NBA champion Shaquille O'Neal that is now on display at Star Plaza outside the arena. The statue, which is 9-feet-tall and weighs 1,200 pounds, was unveiled before the Lakers' home game against the Minnesota Timberwolves on March 24 (the Lakers won that game in overtime, 130-119). It's only a matter of time till Kobe Bryant himself gets his own statue outside STAPLES Center...and I'll be dishin' out 7 dollars (like I did on Wednesday) for parking before I walk over to the stadium to see the Black Mamba immortalized at Star Plaza as well. Happy Friday!

Shaq's new bronze statue at STAPLES Center in Los Angeles...on March 29, 2017.

Shaq's new bronze statue at STAPLES Center in Los Angeles...on March 29, 2017.

Shaq's new bronze statue at STAPLES Center in Los Angeles...on March 29, 2017.

Taking a selfie with Shaq's new bronze statue at STAPLES Center in Los Angeles...on March 29, 2017.

Shaq's new bronze statue with L.A. LIVE in the background...on March 29, 2017.

Thursday, March 30, 2017

MAVEN Update: A Major Discovery on How the Red Planet Became the Barren World It Is Today...

An artist’s concept of a solar storm hitting Mars and stripping ions away from the Red Planet's upper atmosphere.
NASA / GSFC

NASA's MAVEN Reveals Most of Mars' Atmosphere Was Lost to Space (Press Release)

Solar wind and radiation are responsible for stripping the Martian atmosphere, transforming Mars from a planet that could have supported life billions of years ago into a frigid desert world, according to new results from NASA's MAVEN spacecraft.

"We've determined that most of the gas ever present in the Mars atmosphere has been lost to space," said Bruce Jakosky, principal investigator for the Mars Atmosphere and Volatile Evolution Mission (MAVEN), University of Colorado in Boulder. The team made this determination from the latest results, which reveal that about 65 percent of the argon that was ever in the atmosphere has been lost to space. Jakosky is lead author of a paper on this research to be published in Science on Friday, March 31.

In 2015, MAVEN team members previously announced results that showed atmospheric gas is being lost to space today and described how atmosphere is stripped away. The present analysis uses measurements of today’s atmosphere for the first estimate of how much gas was lost through time.

Liquid water, essential for life, is not stable on Mars' surface today because the atmosphere is too cold and thin to support it. However, evidence such as features resembling dry riverbeds and minerals that only form in the presence of liquid water indicates the ancient Martian climate was much different – warm enough for water to flow on the surface for extended periods.

“This discovery is a significant step toward unraveling the mystery of Mars' past environments,“ said Elsayed Talaat, MAVEN Program Scientist, at NASA Headquarters in Washington. “In a broader context, this information teaches us about the processes that can change a planet’s habitability over time.”

There are many ways a planet can lose some of its atmosphere. For example, chemical reactions can lock gas away in surface rocks, or an atmosphere can be eroded by radiation and a stellar wind from a planet's parent star. The new result reveals that solar wind and radiation were responsible for most of the atmospheric loss on Mars, and the depletion was enough to transform the Martian climate. The solar wind is a thin stream of electrically conducting gas constantly blowing out from the surface of the Sun.

The early Sun had far more intense ultraviolet radiation and solar wind, so atmospheric loss by these processes was likely much greater in Mars' history. According to the team, these processes may have been the dominant ones controlling the planet's climate and habitability. It's possible microbial life could have existed at the surface early in Mars’ history. As the planet cooled off and dried up, any life could have been driven underground or forced into rare surface oases.

Jakosky and his team got the new result by measuring the atmospheric abundance of two different isotopes of argon gas. Isotopes are atoms of the same element with different masses. Since the lighter of the two isotopes escapes to space more readily, it will leave the gas remaining behind enriched in the heavier isotope. The team used the relative abundance of the two isotopes measured in the upper atmosphere and at the surface to estimate the fraction of the atmospheric gas that has been lost to space.

As a "noble gas" argon cannot react chemically, so it cannot be sequestered in rocks; the only process that can remove noble gases into space is a physical process called "sputtering" by the solar wind. In sputtering, ions picked up by the solar wind can impact Mars at high speeds and physically knock atmospheric gas into space. The team tracked argon because it can be removed only by sputtering. Once they determined the amount of argon lost by sputtering, they could use this information to determine the sputtering loss of other atoms and molecules, including carbon dioxide (CO2).

CO2 is of interest because it is the major constituent of Mars' atmosphere and because it's an efficient greenhouse gas that can retain heat and warm the planet. "We determined that the majority of the planet's CO2 was also lost to space by sputtering," said Jakosky. "There are other processes that can remove CO2, so this gives the minimum amount of CO2 that's been lost to space."

The team made its estimate using data from the Martian upper atmosphere, which was collected by MAVEN's Neutral Gas and Ion Mass Spectrometer (NGIMS). This analysis included measurements from the Martian surface made by NASA's Sample Analysis at Mars (SAM) instrument on board the Curiosity rover.

"The combined measurements enable a better determination of how much Martian argon has been lost to space over billions of years," said Paul Mahaffy of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Using measurements from both platforms points to the value of having multiple missions that make complementary measurements." Mahaffy, a co-author of the paper, is principal investigator on the SAM instrument and lead on the NGIMS instrument, both of which were developed at NASA Goddard.

The research was funded by the MAVEN mission. MAVEN's principal investigator is based at the University of Colorado's Laboratory for Atmospheric and Space Physics, Boulder, and NASA Goddard manages the MAVEN project. MSL/Curiosity is managed by NASA's Jet Propulsion Laboratory, Pasadena, California.

Monday, March 27, 2017

Photo of the Day: Admiring a Jovian Masterpiece...

Jupiter's cloud tops as seen by NASA's Juno spacecraft from a distance of 9,000 miles (14,500 kilometers)...on February 2, 2017.
NASA / JPL - Caltech / SwRI / MSSS / Roman Tkachenko

Dark Spot and Jovian ‘Galaxy’ (News Release)

This enhanced-color image of a mysterious dark spot on Jupiter seems to reveal a Jovian “galaxy” of swirling storms.

Juno acquired this JunoCam image on Feb. 2, 2017, at 5:13 a.m. PDT (8:13 a.m. EDT), at an altitude of 9,000 miles (14,500 kilometers) above the giant planet’s cloud tops. This publicly selected target was simply titled “Dark Spot.” In ground-based images it was difficult to tell that it is a dark storm.

Citizen scientist Roman Tkachenko enhanced the color to bring out the rich detail in the storm and surrounding clouds. Just south of the dark storm is a bright, oval-shaped storm with high, bright, white clouds, reminiscent of a swirling galaxy. As a final touch, he rotated the image 90 degrees, turning the picture into a work of art.

JunoCam's raw images are available at www.missionjuno.swri.edu/junocam for the public to peruse and process into image products.

Source: NASA.Gov