Mars Express is a European Space Agency probe that’s been orbiting the Red Planet since 2003, returning vast amount of data. Lately it’s been taking some amazing images and video of the tiny Martian moon Phobos, and the ESA just released this amazing footage of the lumpy potato moon passing by Jupiter as seen from the orbiting craft:
How cool is that? Engineers saw this viewing opportunity and actually changed the orbit of Mars Express to be able to see it. Phobos passed a mere 11,400 km (6800 miles) away when these shots were taken, but Jupiter was 530 million km (320 million miles) in the background. That’s why a moon only 27 km (16 miles) across can appear to dwarf a planet 140,000 km (86,000 miles) across! In the diagram here, the relative positions of all four players is shown; click to enbarsoomenate.
Mars Express is a European Space Agency orbiter that’s been snapping away at the Red Planet since late 2003. In August 2010 it took this picture of a bizarre feature on Mars:
[Click to impactenate.]
I would’ve thought this was a canyon of some sort, but in fact it’s an elongated crater! Most likely some large object broke up as it entered the atmosphere of Mars, striking the surface at a low angle and creating a series of craters that merged to form this strange thing. Unlike the triple crater I mentioned last time, this one is pretty frakkin’ big: it’s 78 kilometers (almost 50 miles!) long, 10 km (6 miles) wide at one end and 25 km (15.5 miles) wide at the other. Whatever hit here was pretty big, certainly over a kilometer across before it broke up. Probably several. (more…)
When it was a mere 111 km (66 miles) from the moon, Mars Express took this amazing image:
Click it for the full-res version is a whopping 7800 x 5200 pixel, 13 Mb TIF barsoomenated version. The detail is incredible, with features as small as 8 meters (roughly 25 feet across). Since Phobos is about 27 km (17 miles) long, that’s a lot of detail!
But as regular readers know, I have a thing for 3D red/green anaglyphs, and as the probe passed the moon naturally took stereoscopic images. The folks at ESA put two together to make this jaw-dropping 3D shot of Phobos:
Click it to get 3800 x 2600 pixel, 13 Mb TIF version. You really want to. If you have red/green glasses, this is one of the best anaglyphs from space you’ll see. I’ve never seen something stick out of my screen like this! Also, the details were so sharp that if I shake my head back and forth (like gesturing "no") I can actually see Phobos rotate a little bit, due to the change of positions of my eyes! That was new to me as well, and is very cool. it really solidifies the illusion that you’re seeing an object three-dimensionally.
Mars is an astonishing place, and it’s easy to forget how interesting its two moons are (the other is Deimos, which is smaller than Phobos). Their origins are still something of a mystery, and the surface features on Phobos are not totally understood either. (more…)
The European Space Agency probe Mars Express has been orbiting the Red Planet for just over seven years now, returning vast amounts of information. It looks at Mars, of course, but also the two dinky and weird moons Phobos and Deimos. For example, a little while back it took this phenomenal shot of Phobos over the limb of Mars:
[Click to greatly barsoominate.]
That’s fantastic! Note how dark Phobos appears; it really is much less reflective than Mars. Its origin is unclear, but a popular idea is that it’s an asteroid Mars captured long ago. I’ve never been comfortable with this idea, since capturing an object is extremely difficult. An asteroid moving past a planet will just fly on by unless it is slowed considerably, and there aren’t many ways to do that. If it passes extremely close, the atmosphere of the planet might slow it sufficiently, but that results in a highly elliptical orbit that’s unlikely to last very long. Perhaps Phobos was a binary asteroid, and one of the two components absorbed the extra energy and was ejected, while the other settled into orbit and became Phobos. Maybe it got its start in some other way entirely.
We’ll hopefully learn more when the Russian probe (and lander with sample return!) Phobos-Grunt launches later this year. In the meantime, Mars Express is in an orbit that periodically brings it close to Phobos several times, and we’re entering a new season of passes right now. In fact, it just had a close encounter with Phobos, and word has it the flyby was a success! That means we’ll soon be getting more even interesting and beautiful images of this enigmatic little moon, so keep your eyes open for them.
The resolution is an amazing 9 meters (30 feet!) per pixel. Clearly, Phobos has been through a lot. Mars orbits near the inner edge of the asteroid belt, which may explain how battered its surface is. The grooves were once thought to be ripples from a big impact that created the whopping crater Stickney (not seen in this view, but you can see it really well here), but are now thought to be from boulders rolling around in the low gravity of the moon, perhaps ejected rocks from various impacts landing back down in the feeble gravity.
Note the one winding path going from the upper left to lower right: that looks very much like a boulder bounced its way across the surface! The curvy path is an indication of the changing gravity field of Phobos: it’s not a smooth sphere, but a lumpy potato, so the surface gravity — what you’d think of as "down" if you were standing there — changes greatly depending on position.
They also put together this stunning 3D anaglyph. You can really see the depth of the craters and grooves on the surface. Run, don’t walk, to get a pair of red/green glasses for this one! Phobos really pops out of the screen. The depth and clarity of the 3D is amazing!
This pass of the moon was designed to obtain as much scientific data as possible before the launch of the Russian mission called Phobos-Grunt, which will land on the moon and send a sample of its surface back to Earth for study. Phobos looks an awful lot like an asteroid itself, and its origin is still something of a mystery. More data like these — and obtaining a sample of its surface material! — may clear up its story once and for all.
Yegads. Click to embiggen, and see this in all its glory. This image, taken by the Mars Express spacecraft, has a resolution of 4.4 meters per pixel, meaning objects about the size of a two-car garage can be seen on the surface of Phobos. For comparison, this lumpy, battered moon (named for the Greek word for fear, a companion to Mars) is 27x22x19 kilometers (16x13x11 miles), so even though it’s on the tiny side, this is still a fantastic map of the surface.
And an important one as well: next year, Russia will be launching a probe called Phobos-Grunt (Phobos soil) that will attempt to land on the moon, collect a sample of its surface, and send it back to Earth! These images of Phobos will help the Russians figure out the best place to land.
On the ESA page linked above, you’ll also find a cool 3D anaglyph of Phobos, and if you want to stay up to date on all this, check out the Mars Express blog, too.
You can see that this little moon has been kicked around quite a bit. Those parallel grooves are still a bit of a mystery; they are most likely cracks that formed when Phobos got whacked, creating the 10-km-wide crater Stickney on one end, but that matter is not 100% settled. Maybe these new observations will help end the debate. [UPDATE: Commenter Big Bob points out that the cracks are most likely not due to the Stickney impact! I haven't kept up on my Phobos groovy research, obviously. Also, in the next bit I say more images are coming, but in fact this close passage of Phobos will not yield very high-res pictures, because this flyby is to measure the gravity field around Mars, and the other instruments -- including the cameras -- must be turned off. Oh well.]
And as nice as this image is, we’ll be getting lots better ones soon! So this is a heads-up: closest approach is on March 3, so stayed tuned for more pictures. I’ll post ‘em as I see ‘em.
Phil Plait, the creator of Bad Astronomy, is an astronomer, lecturer, and author. After ten years working on Hubble Space Telescope and six more working on astronomy education, he struck out on his own as a writer. He's written two books, dozens of magazine articles, and 12 bazillion blog articles. He is a skeptic and fights the abuse of science, but his true love is praising the wonders of real science.
The original BA site (with the Moon Hoax debunking, movie reviews, and all that) can be found here.
Contact me: The Bad Astronomer "at" gmail "dot" com
"If things worked the way I wanted them to, any reporter about to do another 'sensational' story on deadly meteors would consult this volume, and bang! common sense would find its way into the news. How strange would that world be?" -- Adam Savage, Mythbusters
"Reading this book is like getting punched in the face by Carl Sagan. Frightening, but oddly exhilarating." -- Daniel H. Wilson, author of How to Survive a Robot Uprising
How cool is that? Engineers saw this viewing opportunity and actually changed the orbit of Mars Express to be able to see it. Phobos passed a mere 11,400 km (6800 miles) away when these shots were taken, but Jupiter was 530 million km (320 million miles) in the background. That’s why a moon only 27 km (16 miles) across can appear to dwarf a planet 140,000 km (86,000 miles) across! In the diagram here, the relative positions of all four players is shown; click to enbarsoomenate.
