The Curiosity rover is still going through its shake down phase, using new equipment and making sure all is well. A few days ago, engineers fired up its 100 mm camera – a telephoto that has a bit more zoom to it than the cameras from which we’ve been seeing pictures. They pointed it to the base of Mount Sharp, the big mountain in the center of its new home of Gale Crater. And what it saw is, simply, breath-taking:
Holy moley. That’s fantastic! [Click to barsoomenate.]
It looks a lot like rock formations I’ve seen in Arizona and Utah… but then, the geologic processes that formed this region are similar. At some point in the past it was flooded with water, and looking at the layering this happened many, many times. The sediments built up and then were worn away over the eons, forming this gorgeous striped sedimentary rock.
Inset here is part of the same scene with distances to various landmarks labeled [click to embiggen]. It looks like there’s the edge of a hill 230 meters away, and then it’s up, up, up, to a series of broad, eroded buttes 16 km away. That would be a fun day’s bike ride here on Earth, but it’s a long way for the rover.
But that is the destination. And it’s not so much the goal as the journey that’s important here. The geology of this region is pretty interesting, and should reveal a lot about the history of the area including how it interacted with water (and what kind of water it was; probably very salty).
You should also take a look at this stunning hi-res wide-angle mosaic of Mount Sharp, too. It’s so wide that if I shrink it to fit the blog it would just look silly. So go look.
These pictures are really exciting. The thing is, the first few times we sent landers to Mars they had to go to relatively boring places – not that any site on Mars is boring, but they had to be relatively flat and free of dangers to the terrestrial machines. Curiosity is the first rover we’ve sent to a place that has real honest-to-Ares geology. I mean, look at it! It’s like the Grand Canyon. But it’s on Mars.
The next couple of years are going to be very cool.
Years ago, I visited the Grand Canyon with my family. The beauty of it was overwhelming, and everything they say about it is true. It’s magnificent.
That grandeur is only amplified by the obvious scientific significance of it. The layers of sedimentary rock, exposed by the eons-long patient erosion of the Colorado river, are a dramatic open textbook of the geological history of our planet, as if the Earth itself is saying "Look here, and learn of the past!"
Learn we have. And the Earth, as we have also learned, is not entirely unique. From millions of kilometers away, another canyon beckons us to uncover a planet’s past.
[Click to engrandcanyonate.]
What you’re seeing here is a topographical model of a small part of a crater floor on Mars: Gale Crater, to be precise, a monster 150 km (90 miles) wide impact located nearly on the equator of Mars. In its center rises a mountain, a central peak common in large impact craters. Surrounding this central peak is an enormous mound of material, rising kilometers above the crater’s floor (see the topographic image below; the ellipse represents an old potential landing site of the Spirit rover). It’s not entirely clear how this mound formed; however, it’s likely that the entire crater was once filled with material laid down as periodic deposits, and that most of it has eroded away, leaving just that lopsided mound.
And like its terrestrial counterpart, the exposed layers tell a history of Mars’s geologic past. Scientists studying those layers using images from the HiRISE camera on the Mars Reconnaissance Orbiter have uncovered a startling feature: while sulfates (deposited by salty water) are seen throughout the layers, clays are only seen lower down, deeper into the past. Clays are only seen where water is abundant, but sulfates alone indicate conditions where water evaporated away.
What the floor of Gale Crater appears to be telling us is that standing water, at least locally, existed long ago on Mars, but later evaporated away. This is consistent with what we have seen in other parts of Mars, of course. Ever since the rovers landed on Mars we’ve seen one piece of evidence after another of standing water in the Red Planet’s distant past.
But there’s something about this news that appeals to me, that touches more than the scientist part of my brain. If I hadn’t told you that first image was from Mars, you might very well think that it was from the Grand Canyon or some other Earthly feature. And it really is a canyon, as you can see from this HiRISE image of the same area:
This image shows the very lower left of the oblique view shown above. It’s upside-down, making features difficult to compare (check out the full HiRISE image of the area to see the whole thing), but the crater floor is at the top of this false-color image, and the mound begins to rise toward the bottom. You can see the canyon carved right into the floor, with sand dunes rippling across it.
Whatever carved this canyon, perhaps hundreds of millions of years ago, perhaps more, tore away the deposited material and revealed all those layers of rock. These layers can be read like a history book written in reverse chronological order, showing us the deep past of Mars, and telling the sad tale of how an entire planet lost its water.
Mars was once more like the Earth is now, though just how much is anyone’s guess at the moment. I doubt it was exactly like Earth; the evidence of water we see indicates it was incredibly salty, far saltier than we have here at home. But still, Mars is a brilliant ochre cautionary tale in our sky. There but for the grace of water go we…