Let me know if you get tired of these… no, wait. Don’t let me know. These pictures from the orbiting HiRISE camera never get old because they’re frakking amazing! Here is another awesome avalanche caught in the act… on Mars!

Holy Haleakala! Coooool. Click the pic to nobly embiggen. And oh yes, you want to embiggen this one.

This may be my favorite Red Planet avalanche of them all. On the left you can see the surface of Mars: that’s frozen carbon dioxide — dry ice — covering the ground. (more…)

Spring is approaching us here in the northern hemisphere on Earth once again, and we are experiencing the annual thaw of the winter ice.

Spring is approaching the northern hemisphere of Mars as well, and with it comes the thaw of carbon dioxide ice. Some of that dry ice sits at the tops of cliffs, and when it thaws it dislodges the material there. The rock and debris on Mars then does the same thing it would do on Earth: it falls. Fast.

And when it does, you get this slice of Martian awesomeness:

Holy scarp!

That’s another avalanche on Mars caught in the act by the HiRISE camera on Mars Reconnaissance Orbiter. I say another, because a few others have been seen, including this spectacular one two years ago, and lots of older ones that left their marks on the Red Planet’s surface.

This one is amazing! You can see the debris falling down the cliff’s edge (the top of the cliff is to the bottom left of the image, and we’re looking almost straight down the cliff’s face) and then creating a plume of dust at the bottom, hundreds of meters below. When HiRISE took this image, the slide couldn’t have been more than a minute old. If you look at the higher-res image (click the image above to embiggen) you can see that there have been a lot of avalanches here in the past, too. The bottom of the cliff has lots of material clearly deposited by fast-moving falling debris.

To be honest, it’s not completely sure that the sublimation (the change from solid directly to gas) of carbon dioxide is causing these avalanches, but it does seem the most likely explanation. Whether it’s dry ice or not, what this shows us directly is that Mars is still an active place. Certainly the surface is undergoing continual (if small scale) modification, with avalanches, meteor strikes, and other processes still occurring even, literally, today.

Mars is a very, very cool place.

If you want to learn more, check out the HiRISE blog, which always has great stuff, including explanations of these extraterrestrial rockslides.

And when you read about Mars and our exploration of it, remember this: it is an entire world, worthy of our attempts to understand it. And that is one of the grandest things we humans ever do.

If someone woke me out of a sound sleep and forced me at gunpoint to say which is my favorite camera in the solar system, they’d probably have to shoot me. But I think that HiRISE onboard the Mars Reconnaissance Orbiter would be in the top three. And it’s pictures like this one that put it there:

[Click to get to greatly embiggened pictures.]

That is not a closeup of my chin before I shave. It’s Mars, a dune field in the far north; at latitude 83.5° to be precise, less than 400 km (240 miles) from the north pole. The eternal Martian wind blows the heavy sand into dunes, and you can see the hummocks and ripples from this across the image. The sand on Mars is from basalt, which is a darkish gray color. The red comes from much smaller dust particles which settle everywhere.

But what are those weird tendril thingies?

In the Martian winter, carbon dioxide freezes out of the air (and you thought it was cold where you are). In the summer, that CO₂ sublimates; that is, turns directly from a solid to a gas. When that happens the sand gets disturbed, and falls down the slopes in little channels, which spreads out when it hits the bottom. But this disturbs the red dust, too, which flows with the sand. When it’s all done, you get those feathery tendrils. Note that at the tendril tips, you see blotches of red; that’s probably from the lighter dust billowing a bit before settling down.

Now, you might think I’m making this all up. How do we know this stuff is flowing downhill like that? Ah, because in this picture we’ve caught it in the act! In this image, a closeup of a region just to the left of center of the big image, you can actually see the cloud of dust from an avalanche as it occurs.

Oh, baby. The cloud is only a few dozen meters across, and can’t be more than a few seconds old.

I love stuff like this. I tend to think of Mars as a stiff, still, unchanging place, but then HiRISE goes and slaps me in the face with something like this. Mind you, this is an avalanche. On another planet. Caught as it happened.

Awe. Some.

We’ve seen this before on Mars, but it’s still shocking and amazing. I can imagine some future settlers on the Red Planet, dealing with the lack of air, bitter cold, dust in all the machinery, radiation hazards from the Sun. And, apparently, they’ll have to dodge landslides too. It’ll be a tough life for sure… but then, I look at pictures like this and think it would be worth it, just to stand on the surface of another world and be able to simply look around.

If we can see this kind of thing from space, with robotic probes, what will humans see when they go there and can kick over some rocks?

This is TOTALLY HAWESOME: an avalanche on Mars was caught in the act by the HiRISE camera.

This picture shows the billowing dust cloud from an avalanche of ice and dust along scarps — sheer cliffs — near the north pole of Mars. To give you a sense of scale, the cloud is about 180 meters across, and about the same distance from the base of the cliff.

Holy cow.

You can see the cliff in the middle of the picture. It’s 700 meters high (2300 feet!) and slopes at about 60 degrees; that’s pretty close to vertical. To the left you can see white carbon-dioxide frost (which is evaporating as spring ensues in the Martian northern hemisphere) at the top of the cliff.

If my (very) rough calculations are accurate, it would take a rock about 20 seconds to fall from the top of the cliff, and would hit the bottom at about 70 meters/second, or about 150 miles per hour. Look out below!

You can read lots more about this on the HiRISE page.

Sidenote: after the disappointing news from HiRISE this weekend, I feel a lot better about this. Totally amazing. I might even say ground breaking.

Update: The HiRISE blog has a more personal take on this as well.