Posted on 09/25/2002 11:48:04 AM PDT by blam
Tough little microbe may be Martian
Russian scientists have suggested that a bug known for its resistance to radiation may have come from Mars.
Tests show it would have taken longer than the 3.8 billion years that life has been present on Earth to evolve such a resistance.
They say Deinococcus radiodurans may have arrived from a higher radiation environment on pieces of meteorite.
The study was carried out by a team from the Ioffe Physio-Technical Institute in St Petersburg.
The microbe has baffled scientists because it can withstand several thousand times the lethal dose for humans.
The Ioffe team told New Scientist that Mars is their prime candidate because possesses much higher radiation levels than the Earth.
They believe the planet's regular cyclical climate swings would have driven evolution faster.
Story filed: 19:06 Wednesday 25th September 2002
19:00 25 September 02
Exclusive from New Scientist Print Edition
A hardy microbe that can withstand huge doses of radiation could have evolved this ability on Mars.
That is the conclusion of Russian scientists who say it would take far longer than life has existed here for the bug to evolve that ability in Earth's clement conditions. They suggest the harsher environment of Mars makes it a more likely birthplace.
The hardy bugs could have travelled to Earth on pieces of rock that were blasted into space by an impacting asteroid and fell to Earth as meteorites.
Deinococcus radiodurans is renowned for its resistance to radiation - it can survive several thousand times the lethal dose for humans. To investigate how the trait might have evolved, Anatoli Pavlov and his colleagues from the Ioffe Physico-Technical Institute in St Petersburg tried to induce it in E. coli.
99.9 per cent deadly
They blasted the bugs with enough gamma rays to kill 99.9 per cent of them, let the survivors recover, and then repeated the process. During the first cycle just a hundredth of the lethal human dose was enough to wipe out 99.9 per cent of the bacteria, but after 44 cycles it took 50 times that initial level to kill the same proportion.
However, the researchers calculate that it would take thousands of such cycles before the E. coli were as hardy as Deinococcus. And on Earth it would take between a million and a hundred million years to accumulate each dose, during which time the bugs would have to be dormant.
Since life originated on Earth about 3.8 billion years ago, Pavlov does not believe that there has been enough time for this resistance to evolve.
Dormant bugs
On Mars, however, the researchers calculate that dormant bugs could receive the necessary dose in just a few hundred thousand years, because radiation levels there are much higher.
What is more, they point out that the Red Planet wobbles on its rotation axis, producing a regular cycle of climate swings that would drive bacteria into dormancy for long enough to accumulate such doses, before higher temperatures enabled the survivors to recover and multiply. Pavlov reported the results last week at the Second European Workshop on Astrobiology in Graz, Austria.
David Morrison of NASA's Astrobiology Institute is sceptical that Deinococcus came from Mars, pointing out that its genome looks similar to those of other Earthly bacteria. But he admits that there's still no obvious explanation for the bug's resistance to radiation.
"It is certainly a mystery how this trait has developed and why it persists," he says.
Stuart Clark
I find it hard to believe that they could be so sure of this statement.
This led them to investigate whether bacteria can live deep in the Earth's crust. Yep. They can. They live by exploiting chemical reactions.
So, is there an alternative to this Russian hypothosis? Yes. Radioactive materials were a lot more prevalent in the Earth's past - but they "decayed" over time to nonradioactive forms. So the first thing is that the early Earth was much more radioactive. The second thing is that it is possible that there are bacteria that are perfectly happy living in the earth right next to radioactive ore. This would tend to increase their radation resistence (in the offspring of the survivors). Heck, the Russians were able to increase radiation resistence fairly quickly in the lab. Living inside radioactive ore for a few million years ought to do it here without requiring a martian explanaton.
Oh wait - I forgot - there is no such thing as evolution. Guess Satan whipped these babies up in his spare time and planted them to confuse those silly godless commmie scientists.
Imagine that.
Application of laws of statistics. They didn't give all the statistical numbers, which would show something like a billion year Confidence Interval with 99% certainty. Nothing is ever 100%.
--Brigader Lethbridge-Stewart, in "Dr. Who"
This one isn't immune to bullets. Feel free to shoot it.
In the meantime, let's make it resistant to heat too, weaponize it and salt nuclear warheads with it (too little coffee makes me bloodthirsty).
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