[X] My Assistant

[remcook]

http://www.timesonline.co.uk/article/0,,2089-1697332,00.html

FAR from discovering life on Mars, Nasa may have put it there. The American space agency believes the two rover spacecraft scuttling across the red planet are carrying bacteria from Earth, writes John Harlow.

Probably isn't the first time either. Can't believe old russian probes had any policy with that respect.

[mike]

If we were to find Earth-like organisms on Mars, we'd have no way of knowing whether they came from Earth-based meteors or whether they've been there for billions of years, regardless of whether probes had ever landed there or not.

As far as a tiny risk having profound consequences, that's true of everything that has some potential for great results - nuclear plants can melt down, jets can crash, gasoline trucks can explode, etc. etc. etc.

If we're not going to do things simply because they're dangerous we should not drive, not leave our house, not eat anything but tofu...

[tty]

If we were to find Earth-like organisms on Mars, we'd have no way of knowing whether they came from Earth-based meteors or whether they've been there for billions of years, regardless of whether probes had ever landed there or not.

Oh, yes we could - the phylogenetic distance would give a good indication how long they had been isolated. Admittedly we don't have a good idea about how fast evolution works on Mars, but separating organisms arriving a billion years ago or in 1975 AD would be easy. Incidentally if there is life on Mars and it is distantly related to earthly life, then it is rather more likely that Mars has contaminated Earth rather than the other way around.

tty

[Sdetton]

Where are you getting these "facts"?  "Thousands of years"?  How do you know that sterilization is superfluous?  Maybe the only earth microb that will survive on mars can't make the long journey on a rock, but the rovers are an exceptable transport. 

ed

What's so different about the rovers that make them better at transporting microbes than pieces of ejecta? The organisms might not survive if they were on the surface of the rock, but they have far better chances if they are inside the rock or maybe in frozen water/hydrocarbons. And the "facts" are actually assumptions based on evidence of how life on earth adapts and evolves. Call it more of an educated guess .

And bravo to dvandorn for some excellent points.

[Guest_Edward Schmitz_*]

What's so different about the rovers that make them better at transporting microbes than pieces of ejecta?

How 'bout time? Seven months vs. seven million years. How 'bout shielding? Parts of the rover are shielded against radiation. How 'bout thermal protection? The WEB is insolated against thermal extremes. How 'bout matterial? vastly different composition. How 'bout food supply? Cork! How 'bout not being blast through the atmosphere by a multi-tera-ton blast?

That's what I came up with in about 2.5 minutes. I'll bet that there are even better differences that I don't even know about.

What's so different? Lots of stuff, that's what.

ed

[Sdetton]

How 'bout time?  Seven months vs. seven million years.

How 'bout shielding?  Parts of the rover are shielded against radiation.  How 'bout thermal protection?  The WEB is insolated against thermal extremes.  How 'bout matterial?  vastly different composition.  How 'bout food supply?  Cork!  How 'bout not being blast through the atmosphere by a multi-tera-ton blast? 

That's what I came up with in about 2.5 minutes.  I'll bet that there are even better differences that I don't even know about.

What's so different?  Lots of stuff, that's what.

ed

Ok, let's examine some of your points.

Time: Can vary. It doesn't always take ejecta millions of years to get there. It can happen within thousands or less depending on the circumstances. Also see the comment about food.

Shielding: The rock can have dense metals or other materials on the surface. Also depends on how deep the microbe is inside. There may also be pockets within to protect against the vaccuum.

Thermal protection: Once again, depends on the makeup of the rock, the amount of time to impact, and other factors. Could make the temps within warmer by maybe a few degrees - not perfect but helps survival.

Food supply: Certain organisms can form a very durable spore (like anthrax for example) when the nutrients aren't at hand. They can even revive after hundreds of thousands of years in such a state ( BBC link )

The only thing the rover seems to have going for it is impact survival - the slow and safe landing of the rover does make it a better mode of transport over the ejecta. But besides that, nothing much.

Anything else?