PDA

View Full Version : Spirit's Big Discovery



Fraser
2007-Dec-13, 02:40 PM
Amazingly, the two Mars rover, Spirit and Opportunity, have been working diligently on the surface of the Red Planet for almost four years now. So far, Opportunity has grabbed most of the spotlight, finding evidence for past water on Mars within months after landing on the smooth plains of Meridiani Planum. While Spirit [...]

More... (http://feeds.feedburner.com/~r/universetoday/pYdq/~3/199744459/)

JESMKS
2007-Dec-13, 05:17 PM
There is also a third option that they don't discuss. The material may be diatomaceous earth, a common silica found on earth and used as the abrasive in many cleansing marerials. Diatomaceous earth is white to cream colored, fine grained and about 90 per cent silica. It is from the accumulation of tests or shells of diatoms. Diatoms are single cell plants or algae that have silica shells and occur in most standing water on earth.

JonClarke
2007-Dec-13, 09:05 PM
There is also a third option that they don't discuss. The material may be diatomaceous earth, a common silica found on earth and used as the abrasive in many cleansing marerials. Diatomaceous earth is white to cream colored, fine grained and about 90 per cent silica. It is from the accumulation of tests or shells of diatoms. Diatoms are single cell plants or algae that have silica shells and occur in most standing water on earth.

Diatoms are quite highly evolved organisms, common only from the Cretaceous onwards (last 145 My). Even Radiolaria, the other common siliceous organism, have been abundant from the Ordovican (last 500 My). Sponges are a bit older, from 540 My (Early Cambrian). But there is no independent evidence for such highly evolved creatures (indeed organisms of any sort) on Mars, or for long standing liquid water as recently as 500 My that would have provided home for such beasties.

Whereas hydrothermal silica is to be expected every where and every time you have rock, ground water (or ice) and a heat source (either volcanism or a large impact). It only takes a few thousand years to form a large hydrotehrmal silica deposit.

Jon

KaiYeves
2007-Dec-13, 10:04 PM
The title of this thread sounds like a good one for a children's book.
"There once was a little robot who went to Mars..."

JESMKS
2007-Dec-14, 06:35 PM
This is in reesponce to Jon's posting. I was taught many years ago that a geologist should put all options (hypotheses) on the table and test and evlaluate them all and then eliminate those that don't meet the observations. It doesn't appear that NASA has considered the diatom option for the origin of the Martiian "high purity opalitic silica deposit"

You mention Radiolaria and sponges as other organic producers of silica. These belong to the animal kingdom and require oxygen to survive. Diatoms, being plants, can flourish in nutrient rich, oxygen free water, possibly like early Martian conditions. You also mention the late (Cretaceous) development of diatoms on Earth is much later than the existence of lakes and sea on Mars. How about this scenerio, the early seas and lakes on Mars teamed with algae growth, and in time diatoms evolved and flourished. With the dissapearance of water on Mars, the diatoms remained as dorment spores in the Martian soil. Sometime during the Cretaceous Period, diatom spores, like the Martian meteorite, made its way to Earth. The spores were still viable and seeded our lakes and seas.
I believe that NASA should conduct some field investigations of silica deposits on Earth and compare their findings to the observations and tests made on Mars. They could examine all types of opalitic silica deposits. I would think that hydrothermal deposits of silica would be consolidated, not friable and would be contaminated with other precipitates. Diatomaceous earth can be of high purity.
One added bit of information, NASA uses a mixture of diatomaceous earth and sand in their sandbox to similate Martian soil conditions to test traction problems with the rovers.