What the heck hit Mars and made this?

[Click to barsoomenate.]

This image is from my favorite Red Planet paparazzo, the HiRISE camera on Mars Reconnaissance Orbiter. It shows three craters, each about 1.5 to 2 km (0.9 to 1.2 miles) across… and they all formed at the same time!

How can I tell? Well, for one thing, if this were a coincidence, with three impacts happening at very different times, then you’d see overlap in the crater rims; the earliest crater would be partially obscured by the later crater, and that in turn by the most recent impact. But that’s not the case here, since the rims aren’t overlaying each other. In fact, the straight walls between them are exactly what you’d expect if you have impact explosions happening simultaneously: the expanding shock waves smack into each other and create a linear feature.

Not only that, but let your eye follow the straight lines between craters up and down, above and below the craters themselves and onto the landscape. You can see that the hellish expanding wall of fire etched itself onto the Martian surface well beyond just the crater rims, and those linear features match the crater wall orientation. I annotated the image here to show you what I mean; the red lines are just outside the linear features.

I can picture what must have happened, millions of years ago over Mars…
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Sometimes, I see an image and do a double-take. This picture sure caused one:

[Click to barsoomenate.]

If I told you those were bacteria under a microscope, you might believe me for a minute or two. But actually, those are sand dunes on Mars!

Yup. It’s funny how bizarre and alien Mars can be. What you’re seeing in this image from the Mars Reconnaissance Orbiter HiRISE camera is actually two different kinds of sand: the dark stuff in the big dunes is actually made of grains of gray basaltic sand. They’re heavy and pile up into dunes. The ripply pinkish stuff between the dunes is made of smaller grains of sand laden with iron oxide — rust! The wind can shape those grains more easily, so they can form more gentle, smaller wavelike patterns. This is also why dust devils on Mars leave such amazing and intricate patterns.

Still, those dunes really look like microbes… and hey, wait a second. There are a set of characteristics that living things share: the ability to consume, excrete, multiply, and show complexity. Sand dunes consume, in a way: the wind brings in more sand to build them up. The excrete, too, by losing sand. They can grow, and split in half, making more. And in point of fact, they do show emergent complex behavior.

Maybe the dunes share more than just appearances with bacteria…could sand dunes actually be [dun dun dunnnnnn] alive^*?

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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