Posted on 09/26/2002 3:12:44 PM PDT by Heartlander
Tough Earth bug may be from Mars
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 traveled 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
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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.
Foolish. A dose of radiation accumulated over a few days or weeks would not have the same effect as the same dose over a hundred million years. Besides, if that's all it took, all life would exhibit a similar radiation resistance; our cell line certainly reaches back hundreds of millions of years, too. The radiation resistance is most likely the by-product of another evolutionary pressure.
New Scientist sensationalism ping.
Assuming the lethal human dose was the MLD, they got the bugs closer to human survivability, but still short. I'd like to see the raw data before I'm too impressed.
The "mean lethal dose" for humans for a one-time exposure to ionizing radiation is around 300 rads (i.e. 3 Gray), that is, 50% of the humans exposed to such an absorbed dose would be expected to die within thirty days with no medical treatment. While it varies from product to product, a typical absorbed dose for the sterilization of disposable medical products (sutures, surgical kits, operating gowns, catheters, etc.) prior to their delivery to hospitals is around 25 kGy (about 40 million times more than a typical chest X-ray, and over 8,300 times more than the human mean lethal dose). An absorbed dose of around 100 Gray (0.1 kGy) is sufficient to kill most insects and parasites, as well as inhibit plant sprouting (i.e. extend the shelf life of onions, garlic, etc.). Stepping up an order of magnitude, an absorbed dose of around 1.5 kGy --> 4.5 kGy is sufficient to kill most bacterial pathogens (except spores) in foodstuffs such as poultry, beef and spices. For example, a dose of 1.5 kGy will kill about 99.5% (and a 3 kGy dose will kill about 99.99%) of the Salmonella in contaminated poultry (the majority of which is contaminated, incidentally). Similar absorbed dose levels are sufficient for eliminating the danger of bacteria such as E. Coli 0157:H7 and Campylobacter jejune. A slightly higher dose (up to 7 kGy) is allowed for frozen meat. An absorbed dose of around 10 kGy --> 45 kGy is sufficient to inactivate bacterial spores and some viruses. The more resistant spores of Clostridium botulinum (responsible for botulism) necessitate a larger absorbed dose of 30 kGy --> 60 kGy. As previously mentioned, the current required absorbed dose for eliminating the danger of anthrax spores is 56 kGy --> 112 kGy. The US legal limits (both minimum and maximum) for commercial irradiation of various foodstuffs are set forth in Title 21, Volume 3, Parts 170-199 of the Code of Federal Regulations (21CFR3).
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.
Lab-induced evolution bump.
Not bad for 9 hours 22 minutes of work!
Certainly not "proof" of the Martian hypothesis. But I wonder what certain creationists think when they can see a species being transformed, by mutation and selection, literally before their very eyes?
Geologic columns...what about the massive canyon on mars---no water!
The size---circumference of the Earth has gotten smaller(although at certain pts. it could have been changing/variable). During collapse large ridges---mountains would protrude upwards! Land wouldn't form evenly...continents would remain at higher levels above water level then plates would dry out---shrink/'sink' producing canyons--basins--ravines...then cooled and hot sediments would form(rise) as the shrink/sink-ing would continue...producing more mountains/hills--'volcanoes'---to fill the receding gaps!
At the Grand Canyon older sedimentary levels are at the top and the fresher/newer ones below...those straight up 'buttes' came out of hole--soft spots in the plates like cake decorations---Ayres Rock like a bubble in a blown tire.
All that erosion/sedimentary crap old age of the Earth is hooie-dooie!
There is not enough dust on the moon to support an old earth dating system!
Yep.
I believe most people disagree specifically with the ‘theory of common descent’.
Survival of the fittest in a record amount of time.
Not enough time though, so the author assumes it came from Mars… Hmmmm. Abiogenesis is happening everywhere, even Venus. It’s really very common. LOL
Why does it look like it does(grand canyon)?
"The reason that it looks the way does is due to the sequence in which the events that help to create it happened. We already know that there was once a very tall chain of mountains in the area that occupied the Grand Canyon. These mountains were, over many millions of years, eventually eroded away to form a level plain. Fluctuations in climate then caused the oceans to move in over successive periods and each time a new rock layer was deposited. The rock layers were deposited one on top of the other and sometimes there were long periods in between in which some of the upper layers were eroded away, sometimes completely."
"We already know that there was once a very tall chain of mountains in the area that occupied the Grand Canyon. These mountains were, over many millions of years, eventually eroded away to form a level plain.
That is called science..."we already know"! Campfire stories! Junk!!
Evolution...tall tales/legends---big lies(no comprehension)!
But the effect is permanent---zombie brains---religion/ideology---BIAS!
Govt school religion---'science'!
Makes shivers run up and down the spine, doesn't it.
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