Curiosity keeps chugging away across the floor of Gale Crater. A few weeks ago we talked to a rock (My Interview with a Martian: A Story of Origins) that it met as it is working its way to the base of Mt. Sharp. I had mentioned that the trip has been a tad boring compared to the early days of Curiosities explorations. However, in the past two weeks the images that Curiosity has beamed back have become considerably more interesting. The sights include several small craters and rock formations that include conglomerates, finely layered rocks and large boulders. Below I show you a few of those images courtesy of the NASA/JPL image catalog (you can see all 89,000 raw images here: http://mars.jpl.nasa.gov/msl/multimedia/raw/)
Our first stop is an image from two days ago. Check out that rock on the right side that looks like it should fall over. It is just begging for someone to kick it over. I was hoping Curiosity would give it a bit of a nudge. How did it get this way? Either it fell from the sky and landing with a pointy end into the ground and got stuck or the ground around it was a bit higher in the past and has eroded around this rock leaving it standing here. The pile of small pebbles below it suggests it may also be conglomerate like our friend from my past post. In which case it may have been less cemented on one side and so eroded more quickly leaving the rock to appear its hanging there. Remember that gravity is not as strong on Mars and so the forces holding the rock up don’t need to be as strong as you might think.
Here is another picture taken from the front camera showing the same balancing rock we saw above. Now we have more context. To the right you can see a concentration of larger boulders on a small mound. This is the edge of a small crater which is just to the right of the image. It would seem very likely that our strange rock originated from that crater and so it was probably tossed in the air several 10s of feet and dropped where we see it today. The crater is filled in with sand and so the large boulders are worn down. So this event probably happened 10s of thousands if not 100s of thousands of years ago. I expect that some soil has been eroded away from around the rock to leave it “hanging.”
Notice also the mountains in the background. These are the rim of Gale Crater. So all this land in the foreground is the floor of Gale Crater. Before this small crate,r that produced this strange rock, could have formed Gale Crater had to form and all the rock layers that the rover is driving over now had to form. Then a meteorite created the small crater and erosion has been taking place since that time.
Addendum: I’ve added the image below that came available two days after I posted the images above. It is a closer look at that strange rock.
There are many targets for imaging on the rover itself. One of these is a penny embedded on the surface. Periodically the rover images this penny so that measurements of dust accumulation rates can be made. Here we see a comparison of the penny from Mars day 34 and Mars day 411 which accounts for approximately 6 months of Earth time. Some of the dust from sol 34 probably comes from dust kicked up upon landing and so doesn’t reflect normal accumulation of dust but the difference between the two dates does represent the atmospheric dust that is settling on everything during this time. Obviously some dust has fallen and this is the dust that is giving the reddish color to everything that the rover sees. The dust must come from erosion from some part of Mars and then deposition onto other surfaces. So we can say that Mars is experiencing some change even if that is very very slow change over time.
Last week the rover took time to take a series of close-up images of a rock outcrop. This is a nice example of a conglomerate that I talked about last time when I conversed with one of these rocks (My Interview With a Martian).
It is still quite a ways away and it will probably take four to six months to get there at the current rate the rover is traveling but those are the dramatic foothills of Mt. Sharp in the distance. Some very strange hills indeed and I am excited for the rover to get a better look at the strange layered patterns we can see from here.
I will wrap it up with a shot that Curiosity took of part of itself. Here are two of the size wheels of curiosity. The terrain here is relatively flat and this large wheels are having no problem rolling over this part of Mars. You can see that the wheels are not left undamaged though. There are many pits on the thin aluminum sections between the tread.