Time-scales Forum: Spacesettlers
Thread: Time-scales
# 3998 bymymail@... on Sept. 3, 2003, 9:12 a.m.
Member since 2021-10-03
Scientists have suggested that tardigrades may have come on meteors from an ancient Mars because their metabolism is adapted to an environment unlike that of Earth. It's hard to see how natural selection could have given it these abilities.
A Scanning Electron Micrograph of a Tardigrade
One of the most resilient organisms known are tardigrades ("water bears"). Tardigrades can go into a hibernation mode - called the tun state - one that is more akin to "suspended animation" whereby it can survive temperatures from -253C to 151C, as well as exposure to x-rays, and vacuum conditions. When you place tardigrades in perfluorocarbon fluid (again while hibernating), at a pressure of 600 MPa, (that's almost 6,000 times atmospheric pressure at sea level) they emerge from the experience just fine . Even the bacterium Deinococcus radiodurans, the most radiation resistant organism known, only achieves this resistance under some conditions such as fast growth and in nutrient-rich medium.
http://www.spacedaily.com/news/mars-life-02f.html
Even more astonishing is the fact that a species of mite called tardigrades, less than half a millimetre long has been found to be able to survive boiling, freezing and exposure to a vacuum.
The results show that these microscopic animals, can withstand pressures of up to 6000 atmospheres by entering a state of suspended animation, which can be maintained for more than a century.
To accomplish this they reduce their body weight by 50% or more, accompanied by an almost total loss of water using a sugar called trehalose to stabilise their cell membranes. Such evidence points towards a re-evaluation of our current beliefs on how essential liquid water is to the development and preservation of life.
http://science.nasa.gov/newhome/headlines/ast27may99_1.htm
"We also need to understand glaciers to know what to look for and how to seek life on the ice caps of Mars," Hoover explained. For example, cryoconite holes can be temporary glacial micro-Edens. Cryoconite is rock debris broken from mountains and rock surfaces by the moving ice and captured in the ice.
When dark cryoconite is transported near the surface of the ice, it absorbs sunlight and becomes warm enough to melt the ice to produce a hole with liquid water, rich in minerals and nutrients from the rock dust, below the rock. For a few hours or weeks, it's springtime on the glacial ice for a world of minute diatoms, cyanobacteria, green algae, protozoa, rotifers, and even animals like tardigrades and nematodes.
http://www.astrobio.net/news/article261.html
From: Michael
To: spacesettlers@yahoogroups.com
Sent: Wednesday, September 03, 2003 3:48 PM
Subject: [spacesettlers] Time-scales
Hi,
>So I hope that efforts at tweaking the Martians continues :)
As long as the equations say so, I (gladly) will :]
>The point is: his definition of terraformed planet is a planet that, after
>terraformation properly said, will naturally stay habitable for hundreds of
>millions of years.
Yes, longer would be better.
Terraforming a planet would involve importing Earth plants and bacteria and
later, fungi and animals. The long-time scale would be needed to make the
planetary ecosystem sustainable. Then, once it is sustainable, allow it to
diversify. This would produce new species and sub-species more suited to
the new planet. Don't forget, people are part of nature, not seperate from
it. If we, as a species, want to live for aeons, we need additional planets
that will last just as long. That is the point of terraforming, sustainable
biodiversity.
>Mars worshipers and me generally think of terraformation as something to stay
>stable during mere historical timeframes...
To what end? What would be the point of terraforming, then colonising a
planet if only to leave again after settling in? You're talking about
colonies that will grow into civilisations, unless you're proposing harsh
and invasive population control. This civilsation, millions of people,
would need to be relocated, dumped on the next planet to consume it's
resources. Or are you proposing to let them all die? or a human lottery?
Make a planet livable, move people in, consume all the planets natural
resources, evacuate millions of people when the environment is so strained
it can no longer support life, leave behind a desolate resource-poor
wasteland devoid of life. That is NOT the point of terraforming. It is a
consumeristic, parastic approach. I don't want people to spread through the
galaxy as a resource consuming disease. Wasn't that the point of the movie
"Indepedance Day"?
>For example some people think Tardigrades came from Mars
Who does? and why would they think that?