I have a Martian mystery for you today, and one that is writ quite large and dramatically. It seems weird at first, then simple next, but when you dig deeper — literally — things get very weird indeed.

It all starts with an out-of-control awesome picture that honestly made me reel back and say "Wow!"

I present to you out-of-control awesome:

Wow!

Click the pic to embiggen. This unnamed crater is about 700 meters (roughly half a mile) across, and sits in the northern mid-latitudes region of Mars. It’s interesting, isn’t it? The multiple concentric bowls of the crater are trying to tell us something, but what?

My first thought, also mentioned on the HiRISE blog, is that this is a coincidental double impact: the big terraced crater was the original impact, then a later, second object impacted almost exactly in the center of the older one, hitting the bulls-eye like William Tell splitting an arrow.

The topography seems to support that; the inner crater has a raised rim, as you might expect from a second impact, and that would be hard to explain in a single impact. The terracing — shelf-like structures sortof like an upside-down wedding cake layering — is seen sometimes when an impactor smacks into layered ground. Imagine a layer of dirt on top of ice on top of rocks: each layer reacts differently to the impact, leaving the circular, concentric shelves in the crater bowl.

Note too that the central crater doesn’t look exactly centered, supporting a second impact.

Case closed… but wait, Your Honor! We have a surprise witness!
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The Mars Phoenix lander touched down near the Red Planet’s north pole in May of 2008. It was designed to investigate the history of water on Mars, digging into the surface soil and examining the chemistry there. It had a limited design lifetime of only a few months, since the onset of Martian winter in the north made weather conditions too severe to continue operations.

The hope was that NASA would be able to revive the lander once spring had sprung. Many such attempts have failed, and we may now know why: new images show the lander may be damaged.

The image on the left was taken in July 2008 with the HiRISE camera on the Mars Reconnaissance Orbiter, and shows the lander in blue. The image on the right was taken just a few days ago, on May 7, 2010. The illumination is similar in the two shots — note the landscapes are very similar looking — but the shadow cast by the lander looks different now. My first thought was that dust built up on the lander, making it look different, but scientists have shown this not to be the case.
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Universe Today is reporting that a recent landslide on Mars looks to be triggered by a small (under 1 meter) rock hitting the surface of the planet. The landslide is less than three years old, and a new impact crater near the top appears to be the culprit.

Go to the UT article to get details. And look at the bigger version there of the image taken by the HiRISE camera; there’s a much larger crater near the bottom of the slide, and you can see where the dust rolled into it and up the far slope of the crater wall, but only partway! It’s yet another amazing shot of the dynamic surface of this nearby world.

The idea of liquid water on Mars is an enticing one. We know life on Earth needs liquid water, and if we find it on Mars… We know there’s plenty of frozen water on Mars; we see it there in abundance. But Mars is cold, and the air is thin, making liquid water on the surface difficult to achieve, let alone sustain.

But there’s been tantalizing evidence. Ever since Mars Global Surveyor got to the Red Planet in 1997, we’ve seen gullies sprinkled here and there. These gullies form on slopes near the tops of the hills, and are clearly the result of something moving downslope and digging furrows. But is that something water, or just sand and dust? The conclusions flip-flop back and forth; I’ve seen papers come out saying water-not-sand and others saying sand-not-water several times.

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Does liquid water still flow on Mars?

We know that in the distant past — like, a billion years ago — liquid water was abundant on Mars. We also know that water currently exists on Mars in the form of ice, sometimes just below the surface (where even small meteor impacts can reveal it). But can there still be liquid water flowing on Mars, even if only for a very, very short time?

Maybe. Just maybe.

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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.