Mid-infrared light reveals a contaminated crust around Ceres
Published 1/19/2017 in Franck Marchis Blog Author Franck Marchis
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... read more ❯

Dunes carving up rock (3D)
Published 1/16/2017 in Lori Fenton's Blog Author lfenton
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 3.2x1.8 km (2x1.13 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) read more ❯

Tortoise and hare
Published 1/12/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: There's a lot of evidence for both fast and slow movement in this 480x270 m (0.3x0.17 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) read more ❯

Crater ejecta on old ripples
Published 1/3/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: Mars rarely does anything without drama. Long ago in this 0.96x0.54 km (0.6x0.34 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) read more ❯

Steno's principles, or "how to make sense of pretty landscapes"
Published 12/26/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: Nicholas Steno was a 19th century geologist, who came up with some principles that are still used today to guide interpretation of exposed sedimentary rocks. The principles seem a bit obvious, but then some of the most profound principles can be like that. Emily Lakdawalla of the Planetary Society describes them in more detail here, with really good examples. You can use these principles to do forensics on a landscape, to see what happened and when. You can see all three principles at work in this image. #1: Stuff makes horizontal layers. (This isn't always true, e.g., dunes and deltas make tilted layers, but most sediments pile up into flat, horizontal layers.) You can see that at work here: A thick layer of dark gray stuff once piled up on a flat surface of brighter stuff. Some of the dark gray stuff has since eroded away, but... read more ❯

The trail of a dune
Published 12/19/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: A low, broad dune occupies the center of this 800x450 m (0.5x0.28 mi) scene, blown by a dominant wind towards the lower left. The slip face on the lee side has several small avalanches, formed as the slope oversteepens (this is how dunes crawl along the surface). Upwind, among other fainter lines, is a prominent bright line: it is a former slip face of this dune, possibly formed from a thick accumulation of bright dust (maybe there was a big dust storm that year). Farther upwind, another dune slowly approaches. (HiRISE ESP_033955_2065, NASA/JPL/Univ. of Arizona) read more ❯

An AGU 2016 Session on Solar System Small Bodies
Published 12/14/2016 in Franck Marchis Blog Author kchris
I co-organized a session for the AGU 2016 meeting entitled "P42A: Solar System Small Bodies: Asteroids, Satellites, Comets, Pluto, and Charon". Below the info on the session and the schedule. We have three invited talks that will describe the New Horizons data of Charon, color of Kuiper Belt Object from a ground-based survey and a theoretical study of the formation of the asteroid belt. Abstract: The composition and physical properties of Small Solar System Bodies (SSSBs), asteroids and dwarf planets, remnants of the formation of planets, are key to better understand our solar system. Increased knowledge of their surface properties and their potential as resources are also necessary to prepare for robotic and human exploration. Hints about the internal structure and composition of SSSBs have been acquired recently thanks to flyby/rendezvous data from space missions, study of complex multiple asteroid systems, or close encounter between asteroids. In this session we will discuss results bringing information on the internal... read more ❯

Them that make ripples and them that don't
Published 12/12/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: Higher ground is to the left. You're seeing a tan layer sandwiched between two gray layers in this 0.96x0.54 km (0.6x0.34 mi) scene. Large ripples have accumulated in the lowest area to the right, which is the floor of an old river channel. Ripples have also formed on the gray upper layer. But not the middle tan layer - maybe it's too fine-grained to erode into sand grains, or maybe it erodes too slowly to allow any eroded sand grains to pile into ripples before they're blown away. (HiRISE ESP_048196_1995, NASA/JPL/Univ. of Arizona) read more ❯

Fall AGU meeting: Detection and Direct Imaging of Habitable Exoplanets
Published 12/11/2016 in Franck Marchis Blog Author kchris
AGU Fall meeting is starting tomorrow. I co-organized a session entitled "Detection and Direct Imaging of Habitable Exoplanets: Progress and Future" to discuss the potential of new and future facilities and modeling efforts designed to detect, image and characterize habitable exoplanets, studying their formation, evolution and also the existence of possible biospheres.  Topics that are covered in this session include signs of exoplanet habitability and global biosignatures that can be sought with upcoming instrumentation; instrument requirements and technologies to detect these markers; strategies for target selection and prioritization; and impacts of planetary system properties, ground-based and space telescope architectures. We have two invited talks, one by George Ricker on TESS and a second one by Shawn D Domagal-Goldman on HabEx, two NASA missions that could play a major role on identification and characterization of Earth-Like exoplanets. Conveners & Chairs: Franck Marchis SETI Institute Mountain View Ramses M Ramirez Cornell University Douglas A. Caldwell SETI Institute Mountain View Location: Room 2020 - Moscone West Schedule... read more ❯

Martian spiders
Published 12/5/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: Martian spiders, or araneiforms, are geological structures found at high latitudes on Mars. The dark splotch with branching arms in this 0.48x0.27 km (0.3x0.17 mi) scene is a good example. They form in the springtime, when bright frost still covers a darker sandy soil, but some sunlight filters through the frost to warm the underlying surface. Sublimation of gas (under the frost but just above the soil) creates enough pressure that little explosions occur like dry geysers, punching through the frost and blowing up sand that then falls back to the surface as a dark splotch. If the wind is blowing when this happens, then the dark splotch is carried a ways downwind, but that hasn't happened in this case. (HiRISE ESP_048189_0985, NASA/JPL/Univ. of Arizona) read more ❯

Published 11/28/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: The dunes climbing over a rocky surface in this 0.96x0.54 km (0.6x0.34 mi) scene are mostly yellow because they're covered (and therefore kept immobile) by dust. The crest of one dune, though, shows recent activity: dark sand has been pushed by the wind up the lower right side, and then shot (cannonball-style) over the brink, where it slowly piles up on the upper left side. This pileup is called grainfall, because that's what the sand grains have done here (rather than sliding downhill, avalanche-style, which is called grainflow). There's a dune on the left side of the image that hasn't experienced this activity, maybe because it's a little more sheltered from the wind. (HiRISE ESP_047779_1655, NASA/JPL/Univ. of Arizona) read more ❯

Bedforms on crater rims
Published 11/21/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: Dunes and ripples most commonly form in topographic lows. But not in this 0.96x0.54 km (0.6x0.34 mi) scene. Here, and in other places on Mars, these bedforms (called TARs) form on plains, and sometimes appear to cling to the rims of craters - which are topographic highs, not lows. It's not clear how this happens: Does the topography of the crater rim provide a wind shadow that allows windblown sediment to accumulate there? Or was there simply more loose material on the crater rims to begin with, allowing these things to form in place? I'm open to suggestions. (HiRISE ESP_047787_1910 NASA/JPL/Univ. of Arizona) read more ❯

Shadows behind boulders
Published 11/14/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: Bright material (either dust or sand) has accumulated in the lee of wagon- to car-sized boulders in this 0.96x0.54 km (0.6x0.34 mi) scene. It's perhaps something like the Rocknest sand shadow that Curiosity visited a few years back. The wind blows from lower right to upper left, carrying along sediment that occasionally gets trapped in the protected areas behind the boulders. These sand shadows aren't very thick, as the underlying texture (polygonal terrain!) is visible through them. (HiRISE ESP_047798_1150, NASA/JPL/Univ. of Arizona) read more ❯

Let's end this political hangover. It is time to fight
Published 11/9/2016 in Franck Marchis Blog Author kchris
It was a tough night … one in which any dreams we may have had of “American exceptionalism” were crushed. Instead of serving, as it has so nobly, for more than two centuries as a beacon of hope and light to people everywhere, this nation will instead see our first African-American president hand the keys to the White House to a low-grade reality TV star who is endorsed by David Duke and the KKK, “alt-right” crazies, and American Nazis. To the horror of many of us, our next president will be someone who explicitly rejects science, reason, and the values we all hold dear—values that are our only hope for moving this country and the world forward. Unfortunately, an America that many of us neither know nor understand decided yesterday that the American Dream is not big enough for everyone—especially not people of color, LGBTs, and struggling immigrants. It was painful to... read more ❯

Dunes and rock hurdles in Gale crater (3D)
Published 11/7/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: Wind from the upper left is blowing dark dunes toward the lower right in this 1.92x1.08 km (1.19x0.67 mi) anaglyph (if you don't have your red/blue 3D glasses handy, you can also check out the black and white 2D version). The dunes are crossing through hurdles aligned to make their progress as difficult as possible, but the dunes nevertheless are slowly making their way through. Ironically, the bright "hurdles" are themselves lithified dunes that are perhaps billions of years old. (HiRISE ESP_020555_1755/ESP_047139_1755 NASA/JPL/Univ. of Arizona) read more ❯

On Mars the wind carves stream channels
Published 10/31/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: This 1.6x2 km (1x1.24 mi) scene mostly shows what wind will do to fine-grained, weakly-consolidated surfaces. It has created topography that further strengthens wind scour in the hollows, which even leave kilometers-long grooves reminiscent of water-carved streams. If this were Earth I'd guess they had been carved by water first. But this is Mars, where the wind is in charge. (HiRISE ESP_046504_1785, NASA/JPL/Univ. of Arizona) read more ❯

The spire in Eberswalde crater
Published 10/10/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: OK, you have to bring out the red/blue glasses for this one. (Or click here if you're missing your glasses and want the black and white version.) Eberswalde crater has some lovely layered deposits, long ago laid down by running water, and since eroded steadily by the wind. The wind leaves behind the most resistant parts (mainly fluvial channels that were more cemented). The center of this image shows a tall spire: the tallest of the flat layers (top of the "wedding cake") is 290 m (950 ft) across and casts a shadow indicating it's 200 m (656 ft) above the next layer down. That central spike is another 70 m (230 ft) taller yet, by itself nearly rivaling the "Totem Pole" in Monument Valley. Check out the rest of the red/blue anaglyph, it's stunning. (HiRISE, ESP_047185_1560/ESP_047119_1560, NASA/JPL/Univ. of Arizona) read more ❯

Windblown: ancient and recent
Published 10/3/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: HiRISE is celebrating 10 years of success by showcasing its first high resolution image, taken back in 2006. Here is a portion of it, shown at 1/4 the full resolution (the scene is 2.5x2.5 km across). I highly recommend downloading the HiRISE image viewer and looking at the whole thing, it's an amazing landscape. The portion shown here has many different ripple-like features, formed by a wind blowing from left to right. Notice that those in the middle and middle-left are a bit fainter: these are ripple-like features that were carved into the bedrock by the wind, and they may be much older than the sharper-edged ones nearby. (HiRISE TRA_000823_1720, NASA/JPL/Univ. of Arizona) read more ❯

Is it windblown or not?
Published 9/26/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: This 480x270 m (0.30x0.17 mi) scene shows what are being called "ridges". Were these ridges once dunes that have now been stabilized and eroded? They have some dune-like characteristics: nearly parallel crests, one slope is steeper than the other, that steep slope seems to have exposed layers, and sometimes the crests meet in what is called a "Y-junction" (based on the letter's shape). But although they're common in some areas on Mars, they're not like any dunes or ripples I'm familiar with. I'm inclined to think they're not ancient dunes, but it's likely that the wind had a hand in their formation. I'm open to suggestions... (HiRISE, ESP_046998_1365 NASA/JPL/Univ. of Arizona) read more ❯

Light and dark
Published 9/19/2016 in Lori Fenton's Blog Author lfenton
A Piece of Mars: This 0.96x0.54 km (0.6x0.34 mi) late winter scene is a study in contrast. The dark top half is uniformly rippled. This is the shady surface of the main windward side of one of Mars' biggest dunes, in Kaiser crater. On the bottom is the sunlit side of the dune, strewn with gullies colored by CO2 frost (white), dark basaltic sand (black), and what may be oxidized fines (orange). (HiRISE ESP_045614_1330, NASA/JPL/Univ. of Arizona) read more ❯