Image: Blue on Mars

Blue on Mars
Image Credit: NASA/JPL-Caltech/University of Arizona

This image shows part of the floor of Rabe Crater, a large impact crater in Mars' southern highlands.

Dark dunes--accumulations of wind blown sand--cover part of crater's floor, and contrast with the surrounding bright-colored outcrops.

The extreme close-up view reveals a thumbprint-like texture of smaller ridges and troughs covering the surfaces of the larger dunes. These smaller ripples are also formed and shaped by blowing wind in the thin of .

One puzzling question is why the dunes are dark compared with the relative bright layered material contained within the crater. The probable answer is that the source of the dark sand is not local to this crater; rather, this topographic depression has acted as a sand trap.

This image was originally released Oct. 24, 2007.


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Mars Odyssey Snaps Rabe Crater Contours

Provided by JPL/NASA
Citation: Image: Blue on Mars (2011, February 17) retrieved 20 October 2019 from https://phys.org/news/2011-02-image-blue-mars.html
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yyz
Feb 17, 2011
"I guess they have shown that it can't be water for some reason other than it is mars, and is supposed to be relatively dry. They didn't mention why they concluded it wasn't water."

This is a poorly written article so I can understand some of your confusion. The image is a *false color* multispectral image taken by the Mars Reconnaissance Orbiter's HiRISE camera. The coloration seen here is not what would be seen by the naked eye (ie true color).

On a separate issue, the presence of (surface) water ice at the at the latitude of this feature is unlikely and AFAIK no signatures for deposits of water ice in this crater have been found.

Feb 17, 2011
Did anybody else notice this picture is from over 3 years ago? (Oct 24 2007

I thought this forum was about the latest breaking news.

Feb 17, 2011
...a sand trap

Great. Freakin' golfers are everywhere nowadays.

Feb 19, 2011
I don't see any martian watercraft so it's OK. That's wild because it looks just like a ocean. I bet someone had to clean their shorts after spotting that picture. I guess they have shown that it can't be water for some reason other than it is mars, and is supposed to be relatively dry. They didn't mention why they concluded it wasn't water.


I mostly like your comment, but they have many tools at their disposal to determine if it's water or not. First off, physics. It is too cold, and the atmospheric pressure is not high enough to sustain liquid water. They also have a spectrometer to determine the chemical makeup. Lastly, it's blue, but no it doesn't really look like water to me.

That picture is ridiculous cool.

Feb 23, 2011
Lastly, it's blue, but no it doesn't really look like water to me.

That picture is ridiculous cool.


As YYZ correctly stated. This is a false-color image. They changed the contrast ratio and the colors so that the contrast between different types of material would stand out. The article even says that it is sand dunes. There's no need for anyone to say anything about how they know it isn't water because that's just stupid. That's like saying that they should also explain how they know it's not a jungle or a city. Completely absurd. The original image would look brown-ish just like the rest of Mars if you correct the colors to match up closely with what the human eye would see. You should understand that all images from Mars are color-corrected and the colors you see in the image are only close aproximations of what you would see if you were there.

Feb 23, 2011
Continued:

The cameras they use in space exploration are designed to be much more accurate than the human eye. The human eye sees best in certain colors and not so well in others, and we have a severely limited range of frequency as well. Space cameras are not the same as your digital camera, which is designed to mimic what you see with your eyes. Space cameras try to see just as much blue and red as they do yellow, and they usually include parts of the spectrum that are invisible to our eyes. Sometimes when you see a pic like the one above what you are seeing is actually a much broader range of spectrum that has been "squashed" into the visible colors we can see. The balance of red/green/blue in the picture will not be representative of real colors unless they specifically arrange the picture colors as such.

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