Back in September I posted an image taken from the Curiosity rover showing Phobos, one of the moons of Mars, crossing the face of the Sun.
That was pretty cool. But this is cooler: video of Phobos transiting the face of the Sun seen from the rover Opportunity on September 20, 2012!
Lest it be overshadowed (HAHAHAHA! Get it?) by Curiosity, remember Opportunity is still going strong after more than eight years on the surface of the Red Planet. These shots from the elder rover are really awesome; Phobos is not even close to being a sphere and you can see its potatoey lumpiness in the animation.
Phobos is about 27 km (17 miles) across its long axis, which is small for a moon. It looks big because it orbits Mars so close in; it’s only 6000 km above the surface. It was actually a bit farther away from Opportunity when these images were taken, making it look smaller than it could be.
In fact, given its size and distance, Phobos has a maximum size in the sky of about a quarter degree, or half the size of our full Moon. As seen from Earth, the Sun and the Moon are about the same size in the sky. But Mars is farther from the Sun, so the Sun looks smaller, about 1/3 of a degree. So even at best Phobos can’t completely block the Sun.
But… Phobos isn’t in a stable orbit. Tides from Mars are dropping it down closer to the planet, making it appear bigger. In a few million years it’ll drop low enough to create total eclipses as seen from the surface of Mars. They won’t last long, since the moon is zipping along pretty rapidly in its orbit. Still though, I have to admit to a bit of delight: creationists like to claim the Earth is special, and we’re the only planet that has the right conditions for total solar eclipses. That’s not even really true right now, and it certainly won’t be once Phobos dips down a bit more.
Of course, once Phobos gets too close to Mars a few million years later it’ll crash into the surface, making the sweatiest apocalyptic scenarios dreamed up by humans look like a warm summer’s breeze by comparison. Nature! It has a way of making our fevered imaginations look like pretty small potatoes.
Image credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ. Tip o’ the rocket crane to Mars Curiosity on Twitter.
I know, it may not look like much, but think about what you’re seeing: a sunset on another world. And those images were taken by a robotic probe that took years to design and build, months to travel the hundreds of millions of kilometers to get to Mars, a harrowing few minutes to descend on a breath of fire through the thin air to land on the surface, and then nearly seven years to travel the landscape long, long past its design specifications.
All that, plus all the amazing science, exploration, and discovery done by Opportunity and its sister rover Spirit… and yet, it’s sometimes the stark beauty of simple things like this that remind us that we have, at least by proxy, placed our feet on other worlds.
I know there are worries here on Earth. But when I see something like this, I remember that the good we do, the awe we feel, and the inspiration we can generate are mighty.
Tip of the pancam to Emily Lakdawalla on Twitter.
Wow, that’s like three puns in one title.
Anyway, scientists have revealed they have found large amounts of carbonates (minerals containing CO3 in them) in rocks on Mars. That’s kind of a big deal: it’s been expected that a lot of rocks would have this compound in them, because there’s lots of carbon dioxide afoot there, and plenty of evidence that Mars was once wet. Those two ingredients lead to carbonates. Yet the rocks looked at closely by the rovers have been strangely devoid of them.
For the rover Opportunity it’s not all that strange; the water on that part of Mars was acidic, and that makes carbonates tough to form. But Spirit is on the other side of the planet, and it was expected it would find carbonates all over the place. Well, turns out it finally has. Some rocks it examined back in 2005 are loaded with carbonates, but it took this long to figure that out because dust that got in the instrument on the rover screwed things up. The scientists had to do some heroic work to tease the data out.
At this point we’ve pretty much exhausted my knowledge of this, but happily we have access to Emily Lakdawalla and her blog, where she goes into detail about the rocks, talking to a scientist involved in all this, too. So go over there and get the rest of this interesting story.
And when you’re over there, don’t forget: we’re talking about a whole planet here. A world. And it was once warmer, wetter, with a thicker atmosphere. Sure, it was over a billion years ago, but it’s always a good idea to keep an eye on Mars when thinking about Earth. There but for the grace of random chance go us.
Oh, I have a very cool anaglyph (red-green 3D images) for you! Stuart Atkinson from the Cumbrian Sky blog has created some fantastic anaglyphs of images from the Mars rover Opportunity as it investigates Concepcion crater. Here are some blocks that look like ejecta from the impact itself:
[Click to embiggen.]
These are beautiful! They almost look sedimentary, which at least makes some sense given that the region Opportunity is roving, Meridiani Planum, was once under water. Closeups of those rocks show they have the famous "blueberries", concretions of jarosite formed by mineral-laden water.
Stuart has lots more pictures he’s fiddled with, too, and it’s well worth your looking around his site. You should also read Emily Lakdawalla’s great description of Concepcion, talking about how we know it’s a fresh crater about 1000 years old. It’s a fascinating read.