White Stuff?
Published on Jun 3, 2008 at 3:21 pm.
3 Comments.
Filed under Mars.
The Phoenix lander has deployed its robotic arm and has carefully scooped up a shovel full of Martian regolith (soil). The camera, of course, is only black and white, but to make it color, three images were taken of the soil as illuminated by three different color LEDs. The images were then put together to make this color image. But, whether black and white or color, several things stand out.
You can see that the regolith is rather granular in nature. I don’t see any obvious rocks or pebbles in the sample. However, it does looks clumpy. Now, the clumpiness is not due to water cohesion. It is far too cold here for water to be liquid. It is not as hard as you’d expect if it were permafrost, either. So, it is something else. Emily Lakdawalla explains that this may be because of cohesion resulting from salty minerals in the soil, giving it a consistency known as duricrust. That could explain much of what we see. It is hard to see from the resolution of the publicly released image, but it appears that the particles in the regolith probably range from dust grains up to sand grains in size. That would be expected on the Martian surface.
But, perhaps the most exciting thing is the bit of white stuff on the right hand side of the image. If you look at the image of the trench that this was scooped from, you can see more white stuff on the right hand side of that image, too.
What’s also interesting is that more white stuff appears underneath the Phoenix lander. The robotic arm was positioned a few days ago to look underneath the lander, and the image below is what it saw.
Phoenix was sent to the northern Martian plains to look for ice. That ice is believed to be perhaps only inches below the surface in this area. So, everyone was leaping for joy when the pictures showed a white patch. After all, if the ice is only inches below the surface, might not the exhaust from the landing rockets perhaps scour the upper few inches off if the regolith is very light? But, white does not equal ice. This may be ice. The white stuff in the scoop and in the trench may be ice. However, it might not be ice. This could also be salt deposits. We now know that Mars once had abundant water, and we also now know that that water was extremely salty (on at least part of Mars). So, if it gets cold enough to freeze, then the salt will still be there. But, ice can sublimate. So, if the upper part of the salty ice sublimates, it will leave behind salt. So, it would not be unexpected for there to be copious salt deposits on top of a frozen sea. And, of course, those salt deposits would appear white.
Of course, this is why the Phoenix lander has other instruments on board besides cameras. It will be able to analyze the white stuff and determine its actual composition. We don’t need to just guess. Everybody loves the wonderful photographs that these spacecraft exploring other worlds send back to us. However, you can only learn so much from the photographs. A single photograph tells you something, but not all that much. All it tells you is what something looks like. You can learn from that, of course. And, naturally, that is where you start. But, you can’t stop there. You can take more photographs, from other angles or under other lighting conditions. That tells you more. But, even better, you can use other instruments: spectrometers, radiation sensors, force sensors, magnetometers, etc. These other instruments let you know the real character of what you are seeing.
So, while I am excited about seeing the white stuff, I am not going to jump ahead of myself and say that it is ice. It may very well be. But, I’ll wait for more data.
-Astroprof
Images courtesy NASA, JPL, UA
Darnell Clayton on June 3, 2008 at 4:19 pm: 1
If its salt, it would be curious to know its chemical makeup, as it could determine whether or not the Martian soil is completely hostile or semi-hostile to Earth plants (the latter of course we may be able to make up for via genetic altering).
Astroprof’s Page » Clumpy Soil on June 10, 2008 at 1:46 pm: 2
[…] all over the intake. But, as things move, not much is sifting into the oven. A few days ago, I wrote about an image of the soil in the robotic arm’s scoop. I commented on the clumps in the soil at the […]
Tito on June 17, 2008 at 11:55 pm: 3
It was most likely a martian that ejaculated on the robot