A Perfect Geyser From Opportunity, Sol 183
Close up look at a typical Martian water source
While data from Opportunity, Sol 183 has been slow in arriving, enough has finally arrived to create a very good image of a typical Martian geyser or periodic spring. While most data arrives within a few sols of acquisition, this is now past Sol 200 (21-Aug-2004 on Earth as of this writing) and some images are just being released.
The only image data there is to work with is from L2, L5, and R1. This is a left infrared image, a left green, and a right violet. Altogether, this is not much, but I have been able to assemble the following false color image and stereo view from those three frames. Note that these are false color and are not implied to be realistic. They are the best that can be done with the data that exists, and are merely an approximation.
| I started
out by creating a synthetic blue frame from the green frame by raising the
contrast and dropping the brightness, then setting the frame to
blue. The L2 frame was used as red data, and the L5 frame is
green. While the color in this image is rather poor, it still close
to what we would expect.
The top left of the stone slab shows a deep depressed slot outlining the stone. The sand around it is extremely clean and all debris is missing from the area. This is one of the signs of sand that has been washed and then vacuum dried. The water emerged, sluiced through the sand, some ran back down into the slot, and the thin air vacuum dried the sand. By contrast, to the upper right we can see where the spherules have gone. They have washed over to the other side of the slab. Notice how concentrated they are. Click the image for a full sized version. The original image data is here at the NASA web site. |
 |
In this magnified view, we see the slot (which is more like a periodic spring than a geyser fumarole) and the results of water flow. Notice how the sand is "cleaned" and has no spherules or small particles. All the small particles have been washed over to the upper right area of the image. The spherules have also been sorted by water flow and are much more dense in the right of the image, just above the rock slab edge.
Now look at the slab itself- there are patches washed clean most likely by the splattering of water See how patchy the sand is on top of the rock slab? And also take note of the absence of spherules in those areas. Some agent has aggressively washed specific portions of the rock slab clean.
Finally, notice the rippled character of the sand inside the slot itself. This is caused by the movement of water. But can we be sure that this in indeed a real opening leading under the rock slab, and not just a groove next to the rock? Yes, by examining the next image.
While this image is a bit large, it was necessary to make it of this scale to carry the full impact of the features. This is a very deep slot that leads under the top edge of the rock slab. Lean back from the monitor and slightly cross your eyes to see the image in stereo.
Click here for a stereo anaglyph of this feature.
What we see is another water source and the clear action of water on the sand and spherules, as well as the stone slab itself. This proves that liquid water is present and active on the surface of Mars today. Wind would soon fill and cover this feature with sand, but clearly this has not had time to happen. With what we know of Martian weather, this feature had to form within a few days at most, and while liquid water will not typically persist for long on the surface of Mars, it is in fact present in episodes and continues to percolate through the soil and bedrock.
The white crust formed in the tracks of the rovers is from ice and salt. Water is mashed from the soil, carried to the surface, and frozen as some of it evaporates. Salts dissolved in the water leave white crystals behind but eventually are mixed with the soil as wind blows sand and dust over it. The implication is that the soil remains wet and can easily harbor microbes or other life forms today.