The Mars Curiosity Rover continues to make its way through the basin of Gale Crater on Mars. I’ve provided periodical updates on its progress as it makes its way toward a large mountain in the center of the crater. Recently it has driven down almost 1000 feet to arrive at nearly the lowest elevation point in the crater. As a result it is now able to observe layers of rock that are below the rock that it has been analyzing for nearly two years. This rock should represent the oldest rock that it available for analysis in its mission.
And very interesting rock it is! Below I share some of my favorite pictures from the main camera on the rover sent back over the past couple of days and provide some short comments. All of these images are provided by NASA/JPL-Caltech. Each day raw images from all of the cameras on board are uploaded to the JPL site for the public to see. You can see them here: http://mars.jpl.nasa.gov/msl/multimedia/raw/
For each image below you can see a much larger version by clicking on the images. Images captions are the file names associated with the images.
This picture above was taken a month before the picture below. This was taken when the rover was sitting up higher looking over the valley between itself and the foothills of the mountain in Gale Crater. The rover is now sitting about one-third of the way up this picture.
On a windswept layer of rocks in a basin surrounded by small cliffs are some fantastically eroded remnants of thinly bedded sedimentary rocks. It isn’t clear if these sediments were laid down in water or by wind but Curiosity has confirmed that the rocks have been soaked in water at some point during their lives.
Some size perspective here. The Curiosity rover is the size of a small car and this is one of the corners of that car.
A chunk of rock that probably rolled or was thrown here from a nearby layers of thinly bedded sediments eroded in the Mars wind. To get the thin shelves of rock the layers of rock must be made of different sized particles of different composition making them erode differently.
The layers of rock that this rock sits on is also composed of thousand of very thin layers that also look like they have been warped as if they were compressed after they were laid down.
Looking up at the bank above a small depression we see that the rocks that once laid above were the rover now sits were also sedimentary rocks. Just above the center middle of the picture you can see that the darker layered rocks are sitting on a thick lighter rock that doesn’t seem to have the saying layering. Again, this suggests changing sedimentary conditions over time in Mars past.
The darker layered rocks near the top clearly are not made of parallel layers as one would expect from sediments laid down in a deep lake. The cross-bedding of the layers suggest small sand dunes or possibly alluvial fans in shallow water.
Here are some other layers rocks in the area. You can see small round pebbles in the rock. These are probably concretions which are the result of minerals which have precipitated out of the rock when the layers of sediment were saturated with water. They are more erosion resistant and so end up eroding out of the rocks and rolling down to the base of the cliffs. These are good evidence of a watery past of these rocks. That water could have been present when the sediments were deposited or that water could have later penetrated the sediments.
Above these thinly layered rocks in this scene we see several large boulders sitting here. This is a most perplexing image to me. All around seems to be an eroded landscape with the rocks having been eroded down to similar levels based on their resistance to erosion. Here we have some very eroded (see below) boulders that clearly have a different composition to the rocks below them. It’s as if someone came along and set these boulders here. I would speculate that these could be rocks that were thrown up here from a nearby meteorite crater. There are other such erratic boulders in the area that Curiosity has seen. Thee boulders probably had sharp edges at one time but have been exposed to wind and have eroded. I don’t think they represent the rock layers that were actually on top of this area long ago because they seem to be sitting very loosely on top of the layers below.
Looking out to where the rover will travel next. The goal is the hills way off in the distance. To get there, Curiosity will have to traverse a region of small valleys and sand dunes. It should be an interesting trip.
Naturalis Historia 