Uncategorized

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... read more ❯

In English Another attack this month, this time in Nice in the middle of the 14 July celebrations. First, the obvious: this attack, which targeted people and families watching fireworks, was despicable and inhuman. Of course, I send my thoughts to the victims and their families as well as to my colleagues and friends who live in Nice. But I am tired of being an impotent witness to this outbreak of violence everywhere in the world, and I absolutely refuse to remain silent. Like many people, I feel like I'm living a nightmare, in a polarized world in which a tiny... read more ❯

A Piece of Mars: Some parts of Mars, like this one, are very dusty. This 1.92x1.1 km (1.2x0.67 mi) area has built up a thick deposit of dust that slowly buries the impact craters until they're mere ghosts of the deep bowls they once were. If you knew the dust fallout rate, you could date the age of the craters. Or if you knew the age of the craters, you could estimate the mean dust fallout rate. (HiRISE ESP_044884_2050, NASA/JPL/Univ. of Arizona) read more ❯

Another day, another video! This time I am posting a video of the binary L5 Trojan Asteroid (617) Patroclus-Menoetius. In collaboration, with the team at the California Academy of Sciences, we have created a model of this interesting binary asteroid system which shares its orbit with Jupiter. In 2001, a group of astronomer discovered that the L5 Trojan asteroid (617) Patroclus is in fact made of two components. In 2006, using Laser Guide Star Adaptive Optics System at W.M. Keck Observatory, we showed that those two components orbit around the center of mass of the system in ~4 days at 680 km... read more ❯

I finally started uploading some of the animations of the talk that I gave last month at the California Academy of Sciences. Today let's watch (624) Hektor, the binary and bilobed largest Jupiter-Trojan asteroids. This is a puzzling multiple asteroid system with a lot of mysteries (eccentric and inclined orbit of the moon, complex shape and structure for the primary, ...).  Our study based on AO observations collected over 8 years was published in 2014. The conclusion of our work is that 624 Hektor is probably a captured Kuiper-belt object and the moon formed a long time ago from the slow velocity... read more ❯

A Piece of the Solar System: This isn't my usual sort of post. But lately my 6 year old kid has been into planets, and thanks to the many informative videos on YouTube, has been reciting various names and numbers about the many worlds in the Solar System. I decided to show him just how much smaller than the Earth some of those worlds are. Here's what I made for him. It's not exhaustive, but it gives a good idea of just how small Pluto is relative to, say, the Moon. The scale is ~2 km/pixel. (Images attributable to NASA... read more ❯

A Piece of Mars: There are two small dome-shaped dunes in this frame (0.96x0.54 or 0.6x0.33 mi). If they got any larger, they'd form slip faces. Any smaller and they'd just be random drifts of windblown sand. Dunes form at a particular size (~125 m in this case) related to the distance it takes for sand grains to accelerate to the background wind speed. This distance is bigger on Mars than on Earth, where the smallest dunes are ~20 m across. (HiRISE ESP_044198_1480 NASA/JPL/Univ. of Arizona) read more ❯

It is official. NSF, together with scientists from Caltech, MIT and the LIGO collaboration will give an update on their effort to detect gravitational waves. What is LIGO? Check out this article published in Arstechnica by Eric Berger. I am not going to speculate on the announcement and will simply wait for it. Joe Giaime a California Institute of Technology physicist who manages the lab and also a professor at Louisiana State University was pretty clear in the Arstechnica interview about the way this group works: “We’re really kind of old school,” he said. “We analyze our data. If there’s anything interesting... read more ❯

Today is December 21, 2015 (northern winter and southern summer solstice on Earth). On Mars it is Ls = 84º, Mars Year 33 (about 12 sols from northern summer and southern winter solstice on Mars). It is sol 1200 of Curiosity's mission on Mars, and the rover is working its way around the southern side of Namib Dune. Part 1 of my previous post shows part of the windward (northeastern) side of High Dune. This time I'll show pictures of the slip face of Namib Dune. The dunes in this part of the Bagnold Dune Field are slowly marching towards the... read more ❯

In a major breakthrough for exoplanet discovery and exploration, the Gemini Planet Imager (GPI) is proving to be one of most powerful and effective instruments ever invented for directly imaging planets in orbit around other stars. An artistic conception of the Jupiter-like exoplanet, 51 Eri b, seen in the near-infrared light that shows the hot layers deep in its atmosphere glowing through clouds. Because of its young age, this young cousin of our own Jupiter is still hot and carries information on the way it was formed 20 million years ago. credits: Danielle Futselaar & Franck Marchis,... read more ❯