Slashdot Mirror
The Dirt On Mars, In Words And Pictures
An anonymous reader writes "The Spirit rover's first soil analysis reveals some puzzling features about Gusev crater. The region seems to contain the greenish silicate mineral, olivine, which usually is considered water-reactive and thus volcanic in origin. For olivine to be found in the soil may point to rock formation during a drier period in martian history, even with strong evidence for sampling in an ancient lakebed. A second puzzle is why the soil seems so crusty. After the rover arm pressed soil down, the top layer of dust hardly moved, a finding that suggests something may be binding the dust like some type of salt or thin cement." For even more and better Mars pictures, read on below.
mlyle writes "I've spent a few hours hacking together some software to deal with the Mars Exploration Rover imagery at JPL. The software puts together a webpage and RDF feed of new raw imagery as it is posted to the JPL site, along with technical information decoded about how the picture was taken. It also produces stereo anaglyphs and color images that NASA has not seen fit to convert and make publically available. Be sure to also check out the ultra high resolution image of the lander as viewed from Spirit."
There's also been an update for the Maestro visualisation and planning thingy. I'm downloading it right now - let's get some more BitTorrent seeds up and running! :)
a color CCD would require a sensor for each of R, G, and B pixel values. By using a monochrome CCD, they could pack as many pixels into the available space and use color filters to determine the RGB values of each pixel instead.
essentially, they are tripling their resolution at the expense of having to take three monochrome pictures each through different color filters to get a single full color picture.
Because conventional colour is too limiting. With filter wheels, there's the possibility of far more scientific data - there's (IIRC) eleven different filters available on Spirit's pancam, instead of the integrated red, green and blue in a consumer-level CCD. There's wide-pass and narrow-pass filters, near-infra-red - they're effectively magic sunglasses which can be used to look for interesting geology from afar.
Surprisingly few spacecraft have taken conventional colour cameras with them. Some of the Voyager colour shots of Jupiter, for instance, are definitely made up of multiple exposures taken at slightly different times - if you look at the red, green and blue channels, you can see how the clouds have moved while the exposures were being taken.
I think the CCDs on modern telescopes are monochrome as well, with particular filters used for looking at interesting wavelengths and things like that. 'Colour' shots are again made by combining multiple exposures...
It's typical for space science applications.
What you want on a space probe is maximal CCD chip area-- not to take things up with filters. So they have a color wheel instead. Also, the filters of ranges that the eye is sensitive to in red, green, and blue is not very useful scientifically.
They have a choice of 8 filters on each of the pancams, and the left filters are in the visible range of light. However, there are caveats, as human visual perception is a complex thing. As a result, colors are going to be off even if a picture is shot with all 7 visual range filters.
The image processing software I've written makes a best guess with 2/4/7 and 2/5/6 filter sets. It is pretty close, but extreme colors are wrong (the red point is shifted by about 30nm) I hope to use the cases where they've shot additional pictures (e.g. magic carpet) to improve things further for selected images in the next couple of days.
Water reactive means it reacts with water and therefore wouldn't form in a wet environment. That means that if you find a rock with this mineral it must be igneous in nature because the other main type of rock formation occurs on seabeds, thus in the presence of water. I'd love for them to find some sandstone or limestone, that'd be a pretty clear indication of water in the past.
It has all the latest Mars Rover info as well, and a direct link to JPL for the latest and greatest pictures and info. www.marsquestonline.org
Go hit it. It's worth a look around.
There is nothing so silly as other peoples traditions, and nothing so sacred as our own.
Of course the show is 50 minutes or so, and the animation you want is in the middle. I taped it when it was broadcast, and I do like the scene you are describing.
Hope that helps.
There is nothing so silly as other peoples traditions, and nothing so sacred as our own.
Two things:
1) Be very wary of judging the apparent size of things in photos taken on another planet. The density of the atmosphere, the nature of the camera lenses used on space missions, and the scale of features your brain uses to guess at size may not all be what they seem.
2) the area around the landing site was deliberately selected to contain as few large rocks that could smash a lander to pieces as it came down as possible. Drop onto really rocky terrain, and you're looking at doing what I believe is technically known as 'a Beagle'.
You've answered your own question here... it's a matter of timing. Olivine rapidly degrades in the presence of water... on a geologic time scale. In human timescales, you don't notice this. That's why you can find green sand beaches on the Big Island - as you note, it's one big active volcano, and the olivine there was relatively recently produced. Gustev crater is thought to be a geologically old feature, and if water was present there, it should have been there a long time ago (based on current theories of the planet's climatological evolution). The fact that that olivine was laid down a long time ago and hasn't shown signs of water induced breakdown, means that water probably hasn't been there since olivine was formed.
Olivine is not found in magmas that are forming at shallow depths which tend to be rich in silica. Moreover, olivine rich magma intruding into the Crust will react with aluminium, silica and alkali metals and change their composition.
So if you find olivine you know the originating magma is coming from deep down and hasn't hung around in the Crust for very long.
Olivine is not terribly stable under wet conditions. Olivine reacts with water to form clays and iron oxide. The results also imply that the olivine bearing rocks have not been heated in the presence of water (such as you would find in the formation of a mountain range), since olivine reacts at high temperatures in the presence of water to form serpentinite and magnetite.
Therefore in the time since rocks were crystallised they haven't been in the presence of water.
Best wishes,
Mike.