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A change of fluids

Cosmic Diary by Lori Fenton - April 17, 2017


A Piece of Mars: Water carved this ~800 m (0.5 mi) wide channel billions of years ago. The water dried up, and since then it’s been sand that flows through here (from the right), building up lovely dunes. A single crater on one of the dunes indicates that they’re not very active (dunes of this type on Mars all seem to be inactive, unlike their bigger, darker cousins). Look closely between the dunes and you might see a few little dots – these are boulders that have fallen, weathered out from the channel walls. (HiRISE ESP_022693_1530, NASA/JPL/Univ. of Arizona)

Another smoking gun in the search for life in Enceladus’ ocean

Cosmic Diary Marchis - April 13, 2017

This illustration shows Cassini diving through the Enceladus plume in 2015.
Credits: NASA/JPL-Caltech

Today, NASA-funded scientists announced a major new step in the search for life on Enceladus, Saturn’s sixth-largest moon, thanks to new data collected by the NASA/ESA Cassini mission.

Enceladus has attracted a lot of interest because it has an active pole that spews jets of material into outer space. During its last flyby over that pole, an instrument on board the Cassini spacecraft detected the presence of a biomarker—molecular hydrogen. This suggests that the ocean we know lies beneath the moon’s surface could indeed contain an ecosystem similar to the ones we find in deep-sea hydrothermal vents on Earth.

During Cassini’s deepest dive through the Enceladus plume, NASA-funded scientists discovered hydrogen gas in the material erupting from the Saturnian moon. Is there life down there? (Image Courtesy of NASA/JPL-Caltech)

Hunter Waite, a researcher at the Southwestern Research Institute in San Antonio, Texas, is the lead author of a paper describing the findings in an upcoming issue of Science. In the piece, the team explains that the molecular hydrogen (H2) content was measured using Cassini’s INMS instrument, a mass spectrometer capable of sniffing the molecular composition of gas that it captures.

During its last flyby of Enceladus on October 28, 2015, the spacecraft grazed the moon’s southern pole at 8.5 kilometers per second, just 49 kilometers above the surface. It crossed the active region where jets spew material from the ocean that we know is located below the icy surface. On three previous flybys, scientists had managed to measure the composition of the jets’ material, and detected molecules of water, carbon dioxide, methane, and ammonia. During the October 2015 flyby, they used the instrument in a mode they hoped would allow them to measure the content of hydrogen molecules in the gas of the vents.

They succeeded—Cassini detected molecular hydrogen.

This is important because the gas is used by microorganisms, known as methanogens, to produce methane from carbon dioxide. Thriving ecosystems seen in the deep oceans of our planet near the volcanic hydrothermal vents of the mid-Atlantic ridge, for instance, depend on the production of energy using this chemistry.

The scientists are very careful when discussing the origin of this molecular hydrogen. They show that the high concentrations measured are not compatible with a geological origin—in other words, such a large amount of molecular hydrogen couldn’t have been stored in the ice shell or in the ocean. Similarly, the scientists are confident that strong radiation on the surface of Enceladus can’t be the source of this molecular hydrogen.  They conclude its source is probably hydrothermal reactions between water and rock, emerging out of active volcanism, as it happens in submarine hydrothermal systems on Earth. The source of this volcanism on Enceladus is still not fully understood, but it is probably related to tidal dissipation in the moon’s core, which is squeezed and warmed as the satellite orbits the gas giant Saturn. As with Europa, a moon of Jupiter, this heat warms up the interior, creating an ocean with hydrothermal activity and surface fractures from which materials can escape in space.

Deep-sea hydrothermal vents in the bottom of the mid-Atlantic ridge when methanogenic-based ecosystems thrive. Similar conditions may exist in the bottom of the ocean of Enceladus. (NOAA Photo Library).

It must be emphasized that the scientists did NOT report the detection of life in Enceladus’ ocean, but rather the detection of molecular hydrogen—the final piece needed to infer the presence of methanogenesis. A model including the characteristics of the ocean (temperature, pH, mixing ratio and composition) supports the idea that methanogenic life could survive in this environment. But thermodynamic models alone are not enough to claim that life is indeed present on Enceladus. In other words, “habitable” does not mean “habited,” and this distinction is important for astrobiologists.

A targeted flyby of Enceladus occurred shortly after this one, on December 19, 2015. The team is probably analyzing more data, but it is not clear that the spacecraft’s INMS instrument was used again to collect observations. With the end of the Cassini mission scheduled for this September, the next step in the study of Enceladus and the understanding its habitability would probably be the design of a mission dedicated to the study of the satellite and the analysis of its jets.

A mission concept called JET was proposed in the last NASA Discovery round of proposals but was not selected. This latest discovery may reactivate interest in sending a spacecraft dedicated to the study of this small (272-kilometer-radius) moon of Saturn. Enceladus and its warm hydrothermal vents could be the place where we one day find life. Microbiological life, most likely, but life—and I for one would be extremely happy with that.

Clear skies,

Franck Marchis

Two directions

Cosmic Diary by Lori Fenton - April 10, 2017


A Piece of Mars: Sometimes I just want to show the interior of a dune field, because it’s full of waves: ripples and dune crests, slip faces, all of which signs of movement. The dunes in this 0.67×0.47 km (0.41×0.29 mi) view have been made by two winds: one blowing from the top of the frame, and a more-recently-active one blowing from the right. Together, these two winds (and gravity) push this sand between a series of hills and down into Coprates Chasma, one of the longest canyons on Mars. (HiRISE ESP_035278_1655, NASA/JPL/Univ. of Arizona)

Where on Mars is this dune?

Cosmic Diary by Lori Fenton - April 03, 2017


A Piece of Mars: This 0.48×0.27 km (0.3×0.17 mi) scene shows a rotund barchan dune. Can you tell from looking at it where on Mars it might be? To me the most obvious feature are the bumpy piles at the bottom of the slip face (at the foot of the dune on the right). They’re probably the remains of avalanches that occurred when there was still winter frost on the dunes. This is a summertime image, so the frost is long gone and the wind is reworking the dune, trying to erase signs of the cold season avalanches. This sort of pattern is best seen in dunes near the north pole. (HiRISE ESP_027674_2650, NASA/JPL/Univ. of Arizona)

A big rock in a big air stream

Cosmic Diary by Lori Fenton - March 27, 2017


A Piece of Mars: Sand pours in from the top of this 1.95×1.95 km (1.21×1.21 mi) scene. The sand piles up and up (here ~115 m or 377 ft high), but ahead (at the bottom) is a mountain poking up. Like water diverting around a rock in a stream, the mountain affects the air flow just upwind of it, causing the sand to move around it. The steep dune slope is a slip face, caused by oversteepened sand avalanching. If you look closely, you’ll see some of those narrow avalanches near the bottom of the slip face (those at the top have been covered by ripples and falling sand). (HiRISE ESP_049045_1760, NASA/JPL/Univ. of Arizona)

More Earth-like views of Mars

Cosmic Diary by Lori Fenton - March 20, 2017


A Piece of Mars: In a recent post (Dunes in a Colorful Hole), I showed some dunes crawling over layered terrain, with a view that looked a lot like some desert regions of Earth. Here’s another spot on Mars (0.95×1.1 km, 0.59×0.68 mi) showing yet more beautiful layers with dunes filling up the valleys. Part of what makes it seem Earth-like is the lack of craters, although if you go looking you’ll see there are some there. It’s hard to tell from here, but this whole scene is inside an old fluvial channel. The layers are thought to be lake deposits from when the river dammed up, ages ago. Since then the wind has taken over, taking apart the layers one grain at a time, and then building up dunes with some of those grains. (HiRISE PSP_010329_1525, NASA/JPL/Univ. of Arizona)

Windblown or not? Probably…

Cosmic Diary by Lori Fenton - March 14, 2017


A Piece of Mars: This 0.95×0.95 km (0.59×0.59 mi) scene shows an eroding surface punctured by some old craters. Long, thin lines seem to form in the wake of many brighter knobs. Are those thin lines windblown in origin? They look like erosional features – things that are left behind when other stuff erodes away around it (not like sand dunes, which are things that pile up over time). If so, they don’t look like typical yardangs, which are streamlined bedrock, formed as sand wears down the rock. But this isn’t typical bedrock – it is easily erodible material. The bright knobs and crater rims are what’s left of a once-higher surface. The darker material may be a lag deposit that has built up as that brighter layer eroded down, leaving behind coarser grains that the wind has a harder time transporting (a similar process has occurred in Meridiani Planum, where the Opportunity rover drove through many kilometers of ripples, which now help protect the surface from erosion). If so, these long thin lines are a very unusual sort of yardang. (HiRISE ESP_016843_1590, NASA/JPL/Univ. of Arizona)

Hills made by wind and ice

Cosmic Diary by Lori Fenton - March 08, 2017


A Piece of Mars: A fluid is something that fills a container it’s put into, and it includes both gas and liquids. This 0.7×0.5 km (0.43×0.31 mi) scene shows hills of sediment left behind by two different fluids (wind and ice). The hill on the left is a rippled sand dune, which has been piled up by the wind as it drops its sandy load. On the right is a layered sinuous hill, leftover from when ice flowed down a slope offscreen to the right. The dune is slowly encroaching on the hill, and will eventually be disrupted by it. (HiRISE ESP_048913_1330, NASA/JPL/Univ. of Arizona)

Dunes in a colorful hole

Cosmic Diary by Lori Fenton - February 27, 2017


A Piece of Mars: Gray dunes have migrated over reddish rock, moving toward a narrowing cleft surrounded by tall tan cliffs. Bright lines on the dunes are exposed internal layers (bones of the dunes, really) that show you where the lee-side slopes once were (so you can tell they’ve moved to the left). The cliffs are made of layered rocks (extra points if you can find the fault), suggesting these are sedimentary layers, laid down long ago in Mars’ geologic past. The whole HiRISE image is worth a long look, it’s really amazing. (HiRISE ESP_049009_1520, NASA/JPL/Univ. of Arizona)

Protected: Wonderful Potentially Habitable Worlds Around Trappist-1

Cosmic Diary Marchis - February 22, 2017

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Who wins in the fight of wind vs. ice?

Cosmic Diary by Lori Fenton - February 21, 2017


A Piece of Mars: This is the crest of one of the largest dunes on Mars (0.5×0.5 km or 0.31×0.31 mi). The wind mostly blows from the right, slowly pushing sand up the windward slope. But frost accumulates on (and probably in) the sand during winter, and sometimes it gets too heavy and slides down the steepest slope (toward the left), carving out big gullies in the sand. And then the wind blows some more, trying to erase the gullies by 1) making ripples, 2) burying the gullies (the featureless blue patches are grainfall, which is a fancy term for sand that fell as airfall), and 3) forming dust devils that leave faint but wide tracks. Who wins this fight, wind or ice? Neither: gravity wins (it usually does). (HiRISE ESP_020876_1330, NASA/JPL/Univ. of Arizona)

Mars’ yin-yangs

Cosmic Diary by Lori Fenton - February 13, 2017


A Piece of Mars: Is this 480×270 m (0.3×0.17 mi) scene showing a 150 m (492 ft) wide yin-yang symbol on Mars? Sort of, maybe, if you blur your eyes and lend me artistic license, but it’s not doing so intentionally. One side of the crater is dark and the other is light. Both have their tone because of windblown material blown from the same direction, but the different materials collected where they did for different reasons. The dark material is probably mafic sand (iron and magnesium-rich, like what’s found near many volcanoes), which was bounced along the ground from the lower right, and collected in the lee of the crater rim. The bright material is much finer-grained, dust carried aloft, and it probably settled down on the far side of the crater, and outside as well, as the crater rim poked into the wind and provided enough shelter to let some of the bright material settle out as airfall. (HiRISE ESP_016496_2000, NASA/JPL/Univ. of Arizona)

The two-faced dunes of Mars

Cosmic Diary by Lori Fenton - February 06, 2017


A Piece of Mars: The focus of this 0.96×0.96 km (0.6×0.6 mi) scene is one of many two-faced dunes on Mars. The bright sunlit slope is one face, formed recently by wind blowing from the upper right. The dark shaded slope is the other face – it’s a little older, formed by wind blowing from the left. Together these two winds alternate, probably in different seasons, forcing the sand into a needle-shaped point that carries sand in a direction that is, give or take, the sum of those two winds. Two-faced dunes like this are rare on Earth, as winds here typically quickly erase older crestlines. (HiRISE ESP_021716_1685, NASA/JPL/Univ. of Arizona)

Dunes + Craters = Mars

Cosmic Diary by Lori Fenton - January 30, 2017


A Piece of Mars: How do you tell when a planetary landscape shows Mars, instead of Mercury or the Moon or Europa? The easiest way to tell is to look for both craters and dunes, like what’s shown here in this 640×360 m (0.4×0.22 mi) scene. Not all martian landscapes have either feature, and there are some other worlds that do have both (Earth, Titan, maybe Pluto, and probably Venus but we need better data…), but it’s a pretty good bet that if you see both features together, you’re looking at Mars. Anyway, in this lovely view, the dark gray terrain (you’ll see boulders if you look closely enough!) is being eroded away slowly, revealing a much older, brighter surface beneath it. Unfortunately for those who would study ancient terrains on Mars, much of that older, lower surface is covered in dunes. But I like the dunes – they give us information about surface erosion rates and wind patterns. One person’s signal is another person’s noise. (HiRISE ESP_047762_1585, NASA/JPL/Univ. of Arizona)

Mars’ giant sweaters

Cosmic Diary by Lori Fenton - January 23, 2017


A Piece of Mars: Sometimes in the floors of small craters, the wind blows in from several directions to produce odd polygon-shaped dunes that look like crochet (maybe Mars is making sweaters for its craters – it is, after all, a cold place). This “sweater” segment is 480×270 m (0.3×0.17 mi) in size (the “stitches” are ~20 m, or 66 ft, across). The smaller interior lines are younger windblown features, that are superposed on the larger structures – their alignment is strongly controlled by the topography of the larger polygonal “stitches”. (HiRISE ESP_017833_1975, NASA/JPL/Univ. of Arizona)

Mid-infrared light reveals a contaminated crust around Ceres

Cosmic Diary Marchis - January 19, 2017

Using a combination of space telescope data, as well as recent data acquired with the SOFIA Airborne telescope and lab experiments, a team of astronomers including researchers from the SETI Institute and Jet Propulsion Laboratory  have revealed the presence of dust of exogenic origin at the surface of dwarf planet Ceres. This contamination likely stems from a dust cloud formed in the outer part of the main belt of asteroids following a collision in recent times. That study challenges the relationship proposed between Ceres and asteroids in the C spectral class and instead suggests an origin of this dwarf planet in the transneptunian region. This study was published on January  19 2017 in Astronomical Journal.

Interplanetary dust particles (IDPs), which form meteors when they cross Earth’s atmosphere, represent the largest fraction of extraterrestrial material accreted on Earth. A team led by Pierre Vernazza, research scientist CNRS in the Laboratoire d’Astrophysique de Marseille (LAM – CNRS/AMU), have shown that IDPs are also an important and continuous source of material captured on the surface of asteroids.

Pierre Vernazza explains that « by analyzing the spectral properties of Ceres we have detected material made up of fine particles of dry silicate called pyroxene. However, thermal evolution models proposed for Ceres have predicted a surface composed of aqueously alterated (e.g., clays, carbonates) which was confirmed from recent observations collected by the NASA Dawn mission. Hence the researchers concluded that it is unlikely that those fine grains of dry material could still be preserved in Ceres’ interior.

The team then searched for the possible source of contamination. Recently, observations from a variety of spacecraft have shown that the zodiacal light has significant structure including dust bands which are associated with debris from particular  asteroid families, resulting from the destruction of a large asteroid. One of these dust bands produced in the main belt is likely the culprit. In particular, the so-called alpha dust band, produced via grinding within the Beagle family (part of the extended Themis family) formed less than 10 Myrs ago and represents a major source of dust in the outer region of the Main Belt. Recent observations also showed that pyroxene dust is a primordial constituent of the Themis family. Hence the alpha dust band is a plausible source of contamination of Ceres and neighboring asteroids.

If the pyroxene observed on Ceres’ surface is of exogenic origin then this challenges the relationship between Ceres and other Main Belt asteroids which has been inferred for decades based on their similar colors in visible light. Astronomers have classified Ceres and 75% of the asteroids in the so-called spectral class C, suggesting a similar  composition.  This result shows that the reality is certainly more complex and the detection of ammoniated clays on Ceres suggest a trans-neptunian origin. Evidence for ammonia or ammonium on another dwarf planet, Orcus,  strengthens that connection.

This study further suggests that the so far unexplained detection of pyroxenes on metallic asteroids* might also originate from a similar dust source. This process likely acts on a global scale at least in the direct neighborhood of the dust band complicating significantly the work of astronomers who want to understand the composition of asteroids from their color.

The SOFIA telescope (credit: DLR/NASA)

« This study resolves a long-time question about the nature of the surface materials inferred from spectroscopic observations in the visible and near infrared, whether they reflect the intrinsic composition of the asteroid or contamination by exogenic material.  Our results show that by expanding the study in the mid-infrared the asteroid initial composition remains identifiable despite contamination at a level of ~20%. »  added Pierre Vernazza

Franck Marchis, planetary astronomer at the SETI Institute also a co-author of this article, stressed out that “The future of asteroid research would greatly benefit from a systematic study of the largest 400 main-belt asteroids. Based on this result, it is clear that mid-infrared spectroscopic observations are key to understand the true nature of an asteroid. Less than 30 of them were observed by the NASA Spitzer and ESA ISO space-based telescopes, and none can be observed with JWST, the next NASA mid-infrared telescope because they are too bright for its sensitive instrument. A dedicated instrument on board SOFIA airborne telescope or a future dedicated space telescope will reveal the true nature of those asteroids even in the presence of contaminations.”

The SOFIA Boeing 747 SP and Franck Marchis, during when of its visit at NASA Ames

  •  Observing in the stratosphere with SOFIA

Observing in SOFIA (credit: F. Marchis)

Observing in SOFIA (credit: F. Marchis)

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The FORCAST Instrument mounted on the SOFIA telescope (Credit: F. Marchis)

The SOFIA program is a partnership between NASA and the DLR (credit: F. Marchis)

 

Dunes carving up rock (3D)

Cosmic Diary by Lori Fenton - January 16, 2017


A Piece of Mars: Get out your 3D blue/red glasses (or look here for a 2D version if you can’t find them). This is a 3.2×1.8 km (2×1.13 mi) scene showing dark dunes carving lanes 50-70 m (165-230 ft) deep into a stack of brighter sedimentary layers. Over time, the sand wears down the rock into yardangs, the elongated remnants of rock the sand didn’t manage to reach. Here we see the process ongoing; perhaps in a few million years there will be nothing left but a few streamlined peaks. Those murdering basterds [sic]. (HiRISE ESP_034419_2015, NASA/JPL/Univ. of Arizona)

Tortoise and hare

Cosmic Diary by Lori Fenton - January 12, 2017


A Piece of Mars: There’s a lot of evidence for both fast and slow movement in this 480×270 m (0.3×0.17 mi) scene.

The tortoise: The rippled surface at the top is high ground: the top of a dune. Wind pushes the ripples toward a steep sunlit slope, creating long thin, dark avalanches that slowly inch the slipface forward. At the bottom of the slope, which is shielded from winds blowing from the top, ripples have been formed by wind blowing from the left.

The hare: Oblivious to both the slow progression of ripples and dunes, 5-25 m wide dust devils have blazed on by, leaving behind erratic trails.

(HiRISE ESP_048592_2070, NASA/JPL/Univ. of Arizona)

Crater ejecta on old ripples

Cosmic Diary by Lori Fenton - January 03, 2017


A Piece of Mars: Mars rarely does anything without drama. Long ago in this 0.96×0.54 km (0.6×0.34 mi) scene, large ripples formed and then, presumably, lithified (turned into rock). Some time after that, an impact formed the crater in the center, throwing debris into an ejecta blanket that covered the lithified ripples. That ejecta blanket sat around long enough to acquire some smaller impact craters of its own. Since then, most of that ejecta blanket has eroded away, exposing the ripples to view once again. (HiRISE ESP_011699_1910, NASA/JPL/Univ. of Arizona)

What the Hack

ENCORE  A computer virus that bombards you with pop-up ads is one thing. A computer virus that shuts down a city’s electric grid is another. Welcome to the new generation of cybercrime. Discover what it will take to protect our power, communication and transportation systems as scientists try to stay ahead of hackers in an ever-escalating game of cat and mouse.

The expert who helped decipher the centrifuge-destroying Stuxnet virus tells us what he thinks is next. Also convenience vs. vulnerability as we connect to the Internet of Everything. And, the journalist who wrote that Google was “making us stupid,” says automation is extracting an even higher toll: we’re losing basic skills. Such as how to fly airplanes.

Guests:

•   Ray Sims – Computer Technician, Computer Courage, Berkeley, California

•   Eric Chien – Technical Director of Security Technology and Response, Symantec

•   Paul Jacobs – Chairman and CEO of Qualcomm

•   Shankar Sastry – Dean of the College of Engineering, University of California, Berkeley, director of TRUST

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•   Nicholas Carr – Author of The Shallows: What the Internet Is Doing to Our Brains and the forthcoming “The Glass Cage”. His article, “The Great Forgetting,” is in the November 2013 issue of The Atlantic.

 

First released November 11, 2013.

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