THE COSMIC DIARY NETWORK

The Three Discoveries of Pan
Published 3/9/2017 in Mark Showalter's Blog Author Mark Showalter
This morning, NASA's Cassini spacecraft obtained the first closeup images of Saturn's innermost moon, Pan. The images show a peculiar body shaped like a "flying saucer". Pan occupies a unique position in the rings, at the center of the 300-km wide Encke Gap. As best we can tell, Pan probably started its life as a more spherical moon, but it subsequently swept up a thick equatorial belt of ring-dust. A smattering of crevasses and craters across the surface add to our view of a moon that has endured a long and dynamic history. Yesterday, Pan was just a "tiny ring-moon"; today, it has been revealed as a world in its own right. Seeing these images has brought back vivid memories of the day way back in June, 1990 when I became the first person to see Pan. That story... read more ❯

Hills made by wind and ice
Published 3/8/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: A fluid is something that fills a container it's put into, and it includes both gas and liquids. This 0.7x0.5 km (0.43x0.31 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) read more ❯

Dunes in a colorful hole
Published 2/27/2017 in Lori Fenton's Blog Author lfenton
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) read more ❯

Wonderful Potentially Habitable Worlds Around TRAPPIST-1
Published 2/22/2017 in Franck Marchis Blog Author Franck Marchis
In May 2016, Michael Gillon and his team announced the discovery of three Earth-sized exoplanets around TRAPPIST-1, an ultra cool M-dwarf star, using the small TRAPPIST telescope at ESO-La Silla, Chile. It was an exciting discovery—yet on that day no one could possibly have imagined that less than a year later they would make another significant discovery involving the same system. But here we are: today, they announced in Nature the discovery of seven potentially habitable Earth-like worlds. The star, named TRAPPIST-1, is a fairly inconspicuous star in our Milky Way. Small (8% the mass of the sun) and cold (half the temperature of the sun), it is a member of an ultra-cool dwarf population that represents 15% of the star population of our galaxy. In 2016, Gillon and his team detected the transit (i.e., the shadow of a planet passing... read more ❯

Who wins in the fight of wind vs. ice?
Published 2/21/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: This is the crest of one of the largest dunes on Mars (0.5x0.5 km or 0.31x0.31 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) read more ❯

Mars' yin-yangs
Published 2/13/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: Is this 480x270 m (0.3x0.17 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... read more ❯

The two-faced dunes of Mars
Published 2/6/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: The focus of this 0.96x0.96 km (0.6x0.6 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) read more ❯

Dunes + Craters = Mars
Published 1/30/2017 in Lori Fenton's Blog Author lfenton
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 640x360 m (0.4x0.22 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... read more ❯

Mars' giant sweaters
Published 1/23/2017 in Lori Fenton's Blog Author lfenton
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 480x270 m (0.3x0.17 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) read more ❯

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 ❯