AI as a Tool for Planetary Defense: How a Computer Could Help Us Make the Right Decisions When Facing An Asteroid Threat
Published 3/8/2018 in Franck Marchis Blog Author Franck Marchis
Last May, a diverse group of astronomers, space agency executives, government representatives, and theorists who study tsunamis and asteroid impacts met for a week in Tokyo to discuss the state of planetary defense.  This group also included a few members of the NASA’s Frontier Development Lab (FDL), an applied research accelerator, aims to foster collaboration between AI experts  and planetary researchers expressly for the purpose of finding solutions to NASA global challenges, including Planetary Defense. The conference took place at Japan’s Miraikan (literally, “Future Museum”), which seemed highly appropriate given that our topic was the threat posed by asteroids and comets, and the actions we might take to address it. After listening to talks by several experts, attendees began a role-playing game which simulated the threat of a ~200m asteroid that might—or might not—strike Earth in ten years. Over the course of a week, we took on the role of government... read more ❯

"Baby" dunes on Mars are big
Published 3/5/2018 in Lori Fenton's Blog Author lfenton
Baby dunes on Mars are pretty big compared to those on Earth. In this 885x512 m (0.55x0.32 mi) frame, there are four dunes of roughly the same size, all of which are about as small as dunes can get on Mars. They're ~180 m (590 ft) across, several times bigger than similar "elementary" dunes on Earth. There's another key difference between Earth and Mars dunes. The avalanching lee slope (the slip face) comes to a point in these dunes. That's because there are two winds forming these dunes, one from the upper right and one from the upper left. On Earth, as winds alternate, they erode the older slip face and create a new one directly downwind, so you wouldn't typically see two crisp slip faces meeting at a point, like they do here. There's something about sand or the movement of sand on Mars that makes slip face creation faster... read more ❯

Dune trails
Published 3/1/2018 in Lori Fenton's Blog Author lfenton
There's so much going on in this 0.75x0.75 km (0.47x0.47 mi) image. You're looking at a broad dune migrating toward the upper right. It's early summer, but this is close enough to the north pole that some winter ice lingers (pale blueish white), amid slumps that have shed down from the dune. The slumps probably form as ice weighs down the dune sand -- they are not seen on dunes at lower latitudes, where ice is less common. The upwind side of the dune is interesting as well. The dark dune slowly migrates forward, leaving behind bits of itself (sort of like how a snail leave a trail of slime). Those left-behind bits have somehow formed into a bright surface -- I'm not sure why it's bright, but it is being slowly being broken into a polygonal shapes and eroded by wind scour, both of which are processes that are common... read more ❯

Ius Chasma dunes: they move
Published 2/20/2018 in Lori Fenton's Blog Author lfenton
Many dunes on Mars are actively migrating, like these dunes (view is 0.4x0.5 km, 0.25x0.31 mi). These are found deep in Ius Chasma, one of the Valles Marineris. These dunes slowly migrate toward the right, pushed by winds blowing from the lower and upper left.       Comparing this recent image with the first HiRISE image taken ~10.5 years ago (that's ~4.4 Mars years) shows development of a crest linking these two dunes, indicating the wind from the upper left has been most active over the last few years. Click on the grayscale image to the left to see an animation of this change. If you want to learn more about Valles Marineris dunes, you can read about them in this paper by Chojnacki et al. (2014). (HiRISE ESP_053595_1725, NASA/JPL/Univ. of Arizona) read more ❯

Where dune fields begin
Published 2/12/2018 in Lori Fenton's Blog Author lfenton
This is the upwind edge of a dune field (825x625 m, 0.51x0.39 mi). Winds blow down a cliff (offscreen) from the lower right, blowing sand toward the upper left. Elongated dunes have formed parallel to the resultant wind direction, only avalanching into slip faces once enough sand has piled up (there are two slip faces at the upper left). The tan/black mottling shows where tan dust has settled or been removed from the dark sand by recent winds. Large grains are heavier and harder for the wind to move, so they form into ripples (with a 10 m or 33 ft spacing) that trail behind the dunes - ripples like these are common on the upwind edge of dune fields on both Earth and Mars. (HiRISE ESP_053594_2610 NASA/JPL/Univ. of Arizona) read more ❯

Mars' "Type A" wind
Published 2/5/2018 in Lori Fenton's Blog Author lfenton
The busy, busy wind has moved a lot of things to make this 0.6x0.85 km (0.37x0.53 mi) landscape. First it built a big dark dune, covering it and the surrounding surface with ripples. Then it dumped a bunch of bright yellow dust all over everything, maybe the result of a nearby dust storm, or maybe just gradual fallout in a quiet season. And then it made some whirlwinds into dust devils that scribbled away some of the dust, revealing the dark dune surface. (I'll also note that when turned upside down, this looks like an interesting one-shoulder dress with a unique abstract pattern. Someone should go make this.) (HiRISE ESP_053195_2305 NASA/JPL/Univ. of Ariz) read more ❯

The superbloodmoon and nachas
Published 1/31/2018 in Lori Fenton's Blog Author lfenton
I set my alarm for 5:30 this morning. Sometimes I skip lunar eclipses, but I do try to see them if they're total, and if I think the sky might be cloud-free (which it often isn't in the Bay Area of CA, as low-lying marine clouds typically roll in overnight). My 8 year old is into astronomy and heard about the eclipse from one of his favorite Youtube science channels for kids (can't remember the name of it or I'd share - I'll ask him and update later on). Last night he asked me to wake him up, and I agreed, although last time I tried to do something like this he just grunted and went back to sleep. So at 5:30 my alarm went off (and so did my husband's - great minds think alike, although he went back to sleep once he realized I would deal with the... read more ❯

Smash! Whoosh...
Published 1/30/2018 in Lori Fenton's Blog Author lfenton
A Piece of Mars: The dark splash pattern in this 0.9x0.9 km (0.56x0.56 mi) scene (click on it for a better view) is the site of an impact crater that appeared between images sometime between August 2006 and March 2010 (Smash!). The main crater is ~7 m (23 ft) across. Impacts smash a little ways into the ground, digging a hole and throwing out stuff that was once buried. Here, the buried stuff is darker than what's right at the surface. There are a lot of other similarly sized craters here, but they no longer have dark ejecta surrounding them. What happened to it? A clue comes from the dark and bright wind streaks in the surrounding terrain, with bright trails flowing in the wakes of craters (Whoosh. . .). Previous HiRISE images from 2010 and 2015 show different wind streak patterns, indicating these patterns change on a timescale of... read more ❯

406 stars observed with GPI
Published 1/24/2018 in Gemini Planet Imager Author Franck Marchis
In November 2014 we set out to observe 600 young, nearby stars with the Gemini Planet Imager (GPI) and the Gemini South telescope. Three years later, the survey has achieved a milestone with more than 400 targets observed. Each frame in this movie shows an image from GPI. The star itself is partially blocked by a mask known as a coronagraph. Together with adaptive optics correcting for turbulence in the Earth’s atmosphere, and advanced image processing, we can  see the stellar neighborhood where Jupiter-like exoplanets, brown dwarfs, and circumstellar disks could be present. 406 stars observed with GPI from Franck Marchis on Vimeo. No instrument is perfect, so every star is surrounded by a residual halo of speckles and noise. But other frames show real astronomical sources. In some frames, the round image of another star is present - a binary companion star or a chance alignment of a distant background star. In... read more ❯

Arnus Vallis, Mars
Published 1/22/2018 in Lori Fenton's Blog Author lfenton
A Piece of Mars: This is a section of Arnus Vallis (scene is 1.25x1 km, 0.78x0.62 mi). It's a >300 km long valley that was carved out, not by water, but by lava, long ago. Since then the wind has taken over. The left wall of the valley seems to have layers etched into high relief by wind scour; the floor is covered by ripples (TARs, really). But what I love most about this valley is that along the right (east) side, a long dune extends for much of the valley's length (it's why you don't see layers on the eastern wall). You're looking at a small section of what could be the longest dune on Mars. You can read more about the geology of this valley in this paper. (HiRISE PSP_007187_1920, NASA/JPL/Univ. of Arizona) read more ❯

Varying wind directions
Published 1/18/2018 in Lori Fenton's Blog Author lfenton
A Piece of Mars: This 0.5x0.4 km (0.31x0.25 mi) scene shows two dunes near the north pole. The shape of the dunes indicates two main winds: one blowing left to right (which makes slip faces on the right side, one of which still has some bright white ice on it), and a secondary wind blowing from the lower right to upper left (elongating the upper "corners" of these dunes). The two lee sides are marked by yellow patches, where bright dust falls out of the atmosphere, accumulating in areas of relative calm. But if you look at the boulders (the largest of which is ~4m across, about the size of a subcompact car), you'll see that a third wind blowing from the upper right to lower left has left some bright streaks in the wake of the boulders. This third wind isn't persistent enough to shape the dunes, so it... read more ❯

Dunes with comet tails
Published 1/8/2018 in Lori Fenton's Blog Author lfenton
A Piece of Mars: The north polar dunes in this 575x325 m (0.36x0.2 mi) scene are made of dark sand covered by bright winter frost (which will soon sublimate away, as this image was taken in late spring). To the right of the dunes extend pale yellow bumpy hills, making the dunes look like they have little "comet tails". What's going on here? These dunes are migrating towards the left, so the tails are what they leave behind. The dunes are located very far north, where the ground is always frozen. Ice freezes the lowest parts of the dunes, so that as the upper sections can be pushed downwind, the lower sections remain locked in place behind. This can happen on Earth too, but here it's usually the water table stabilizing the lower portions of the dunes (and many of the thick continental sandstones, like the Navajo sandstone, were built... read more ❯

Fuzzy dunes
Published 1/2/2018 in Lori Fenton's Blog Author lfenton
A Piece of Mars: The dunes (or maybe they're ripples) in this valley appear to be fuzzy (the view is 625x775 m, 0.39x0.48 mi). They're not really fuzzy, but it's not actually clear what's going on. They seem to have smaller ripples superposed on them, and maybe bright dust has settled into the troughs between ripple peaks, so that they take on a striped, feathered look. It's unlike anything I've seen on Earth. (HiRISE ESP_052776_1785, NASA/JPL/Univ. of Arizona) read more ❯

Buried by ejecta
Published 12/26/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: To see this one well you'll have to click on the image. At the lower right, a 240 m (787 ft) diameter crater formed when a bolide hit the surface, throwing out ejecta on the surrounding terrain. Zooming in, you can see that the ejecta has a distinctive rough surface. Farther from the crater there are smooth patches where ejecta didn't fall. What I like about this is the many small bedforms (ripples), some of which are covered by ejecta and some of which aren't. Closer to the crater, you don't see so many of these bedforms because the ejecta is thick enough to have buried them. The crater itself is fairly "young" for a geologic feature on Mars, but enough time has passed to allow small bedforms to accumulate inside it (ripples like these don't form overnight). (HiRISE ESP_052794_1545, NASA/JPL/Univ. of Arizona) read more ❯

The mysterious bright streaks
Published 12/18/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: Some things just go unexplained (so far, anyway). Here's a mysterious bright streak (scene is 1.2x1.8 km, 0.75x1.12 mi) concentrated between two sets of ripple-like bedforms. It looks sort of like a river, but it's on flat terrain and it's not water. It's part of a larger set of bright streaks that you can see throughout the top of this broader CTX image (the bright streak shown in detail here is visible as a distinct white stripe on the floor of a crater). My guess is that at some point, probably at least several million years ago, a bunch of fine bright silt was blown towards the north-northwest, settling in a few places. I'm guessing it's silt (finer-grained than sand) because it didn't form dunes, and it's not as fine as the clay-sized dust that blows into dust storms because this stuff wasn't completely blown away... read more ❯

Dunes in a row
Published 12/11/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: Look at the alignment of the ~100 m dunes in this 713x750 m (0.44x0.47 mi) scene. How do dunes form in such straight lines? And why don't they always do that? It's likely that these dunes were once long ridges stretching from the lower right to upper left. The shape of the slip faces suggests they're formed from two winds that blow from similar directions, both of which push sand toward the upper left. To stay stable, this sort of dune needs a constant influx of sand from upwind (from the lower right), but if that flow of incoming sand lessened, then a long dune would be forced to break up into a series of smaller dunes. That may be what's happened here. Check out the whole image, and you'll see other long ridges that haven't yet broke up into smaller dunes. (HiRISE ESP_052798_2565, NASA/JPL/Univ. of... read more ❯

Ripples of rock
Published 12/4/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: To the upper right of this 0.85x0.6 km (0.53x0.37 mi) scene is a flat-lying plain strewn with large ripples. To the lower left is a rugged hill with gray rock laced with white veins (this might be part of an impact megabreccia identified nearby in Holden crater). Notice that some of the ripples on the rugged hill are also veined - this is evidence that they are actually eroded into the bedrock, rather than fine-grained deposits like their counterparts on the plain. It's not yet clear how these "Periodic Bedrock Ridges" form, and they may be unique to Mars. (HiRISE ESP_052789_1520, NASA/JPL/Univ. of Arizona) read more ❯

Athena Coustenis, Full Curriculum Vitae
Published 11/27/2017 in Athena Coustenis Author Athena Coustenis
Dr HDR Athena Coustenis Observatoire de Meudon 5, place Jules Janssen 92195 Meudon Cedex France PROFESSIONAL STATUS Athena Coustenis is Director of Research 1st class with the National Centre for Scientific Research (CNRS) of France, working at Paris Observatory in Meudon. Affiliation: Paris Observatory, PSL, CNRS, Sorbonne Université, U. Paris-Diderot Her specialty is Planetology (exploration and study of the Solar System from ground-based and space observations). She is currently the Chair of the European Science Foundation Space Science Committee (ESF-ESSC). EDUCATION/DEGREES 1986: Master in Astrophysics and Space techniques, Univ. Pierre et Marie Curie (UPMC), Paris 6 1987: Master in English Literature, Univ. Sorbonne-Nouvelle, Paris 3 1989: PhD in Astrophysics and Space techniques, thesis, Univ. Pierre et Marie Curie (UPMC), Paris 7 1996: Habilitation to Direct Research (HDR), Univ. Pierre et Marie Curie (UPMC), Paris 7 Languages spoken: Greek (maternal), French (native level), English (Proficiency), Good command of Italian PROFESSIONAL HISTORY Since Oct. 2013: Director of research, 1st class, CNRS, at... read more ❯

The corpse of a dune
Published 11/27/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: The rippled darker patch in this 600x600 m (0.37x0.37 mi) scene is the former site of a sand dune. This is one of a few "dune corpses" found just upwind of a dune field in Holden crater. The dunes are migrating to the south and east - you can see that the arc of this former dune opens to the south, the way a barchan slip face would. This dune is what's left behind after most of its sand has migrated downwind. (HiRISE ESP_052367_1540, NASA/JPL/Univ. of Arizona) read more ❯

List of publications
Published 11/26/2017 in Athena Coustenis Author Athena Coustenis
Director of Research 1st class, CNRS, France Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique (LESIA) Observatoire de Paris-Meudon 92195 Meudon Cedex FRANCE List of publications download a PDF List of publications and communications 230 publications, 134 peer-reviewed publications, more than 5700 citations, H=42   Thesis Coustenis, A., 1989. L'atmosphère de Titan à partir des observations infrarouges de Voyager. Doctorat de l'Université Paris 7, defended on 17 May 1989.   Habilitation Coustenis, A., 1996. Atmosphères et surfaces des petits corps planétaires. Habilitation to direct Research (HDR), Université de Paris 7, defended on 20 December 1996.   Publications in peer-reviewed journals Coustenis, A., Bézard, B., Gautier, D., 1989a. Titan's Atmosphere from Voyager Infrared Observations: I. The gas composition of Titan's equatorial region. Icarus 80, 54-76. Coustenis, A., Bézard, B., Gautier, D., 1989b. Titan's Atmosphere from Voyager Infrared Observations: II. The CH3D abundance and D/H ratio from the 900-1200 cm-1 spectral region. Icarus 82, 67-80. Lellouch, E., Coustenis, A., Gautier, D., Raulin, F., Dubouloz, N., Frère, C., 1989. Titan's atmosphere and hypothesized ocean: a reanalysis of the Voyager 1 radio-occultation and... read more ❯