[X] My Assistant

[dilo]

This mosaic of 4 Panoramic frames from Sol442 show a strong increase in density of rocks, even big ones! Don't know if could be an issue for further movements toward the hill top?

[Bill Harris]

So how long do we wait? Say MSL or some other rover in the next 20 years finds...

I do not know. As a child of the space age growing up in the 1960's I have long dreamed of zipping up a spacesuit and clomping around on Mars. But now that we are wiping our feet on Mars' doormat I have reservations about leaving our molecular footprints until we find out what is there.

--Bill

[Mode5]

Great pics Dilo, thank you for posting. The 3rd one down on the right is my favorite. The split in the rock with the inner surface exposted is begging for a close-up.

Mode5. it seems they heared you!

Too cool Dilo! Thanks for the followup. That piece hanging out looks out of place or had some heavy weathering. Are there any theories on it?

[paxdan]

So how long do we wait? Say MSL or some other rover in the next 20 years finds...

I do not know. As a child of the space age growing up in the 1960's I have long dreamed of zipping up a spacesuit and clomping around on Mars. But now that we are wiping our feet on Mars' doormat I have reservations about leaving our molecular footprints until we find out what is there.

--Bill

Earth and Mars have been swapping material since the formation of the solar system. We've found mars rocks here, even a bit of phobosite. And while earths gravity well is deeper than that of mars, I don't doubt that with the rich biosphere which has existed here and the near ubiquity of microorganisms in the first couple of Km's of the earths crust that at least a few bacteria have made the ride. I am certain also that we have sent life. I worked for a year as an undergrad in a Category 3 containment lab working with nasty pathogens, and while this doesn't make me an expert on biocontamination. If there's one thing I know it is that bacteria are tough little buggers and they get everywhere. I am confident that we have sent life (or its remnants) to mars on every craft dispatched so far.

In short I think the debate as to whether we should risk contaminating is moot. In fact I think the use of the word contaminate is wrong as it implies that some form of containment is being breached. Well those millions of kilometres of vacuum have been breached thousands (if not millions, or billions) of times during the last 4.5Gyr and we've done a good job in the last 45. It just isn't a pristine planet.

When we go to mars, of course we should do everything possible to minimise the exposure to our biota, but not at the expense of our next small step.

[cIclops]

<snip>

In short I think the debate as to whether we should risk contaminating is moot. In fact I think the use of the word contaminate is wrong as it implies that some form of containment is being breached. Well those millions of kilometres of vacuum have been breached thousands (if not millions, or billions) of times during the last 4.5Gyr and we've done a good job in the last 45. It just isn't a pristine planet.

When we go to mars, of course we should do everything possible to minimise the exposure to our biota, but not at the expense of our next small step.

Yes, unsubstantiated speculation about contamination risks should not interfere with exploration, however the assumption that bacteria can survive ten of thousands of years exposure to solar radiation and hard vacuum in space, plus atmospheric reentry also lacks evidence.

[Bill Harris]

Well those millions of kilometres of vacuum have been breached thousands (if not millions, or billions) of times during the last 4.5Gyr and we've done a good job in the last 45. It just isn't a pristine planet.

Agreed. I _do_ think that we need to approach this cautiously in case irreparable harm is caused. Although Earth, Mars and neighbors have been exchanging material for eons, there is a difference between sending a rich source of biological material to Mars as opposed to a bug hitching a ride on a rock. Just as there is a fundamental difference between a natural process and a manmade action. There have been natural mass extinctions on Earth since time began, but if humans caused a "nuclear winter" or other catastrophe that would be looked at unfavorably.

I agree in principle, just be careful!

My own career has been devoted to minimizing the environmental impacts of mining on the surrounding countryside, and as such I look at myself as a _environmental_realist_, as opposed to an environmentalist.

--Bill

[Gray]

Hmm, this topic seems to have split into two conversations; one about rocks the other about human exploration of Mars. I wonder if we should separate the two; or is everyone OK with the contrapuntal discussions.



Mode5,

The image you noted looks really neat. The rock in the bottom center of the picture looks as if it's crumbling from the bottom up. Perhaps the rocks are experiencing very slow mechanical weathering in a zone close to the soil. Could this be the effect of frost action over long periods of time?

[paxdan]

<snip>

In short I think the debate as to whether we should risk contaminating is moot. In fact I think the use of the word contaminate is wrong as it implies that some form of containment is being breached. Well those millions of kilometres of vacuum have been breached thousands (if not millions, or billions) of times during the last 4.5Gyr and we've done a good job in the last 45. It just isn't a pristine planet.

When we go to mars, of course we should do everything possible to minimise the exposure to our biota, but not at the expense of our next small step.

Yes, unsubstantiated speculation about contamination risks should not interfere with exploration, however the assumption that bacteria can survive ten of thousands of years exposure to solar radiation and hard vacuum in space, plus atmospheric reentry also lacks evidence.

What it lacks is direct evidence. All the components are there. If you were a bacteria check out this as your spacesuit, makes sense seeing as the majority of big impacts are going to take place in the ocean. As for solar radiation i have no idea how big a rock you would need to preserve a sporulated bacteriaum inside a salt crystal, i'm not even going to guess. Reentry, in comparision, is the easy bit. It's ram pressure that causes the meteors to glow not friction, and the interior temps of meteorites above a certain size remain low. Below a certain size they slow to terminal velocity in the atmosphere and impact at a few hundred kph.

Really the hard part is the shock and heating casued by the impact that would be required to blast them of the earth in the first place.

<end panspermia related threadjack>

[David]

By the way, keep in mind that if you're going to adopt the alternative of just putting a crew into orbit around Mars and having them teleoperate surface-exploration robots without that maddening radio time lag, you can explore Venus in exactly the same way.  And it's closer (if less scientifically interesting, and more exposed to solar particle radiation and X-rays...)

If there were no intention of putting humans on the surface Mars, then I don't see any particular advantage to prioritizing a human mission to Mars. It seems to me that if we want to move in easy steps from moon landings to human exploration of other parts of the solar system, the natural sequence would be:
1) Near-earth asteroid rendezvous/landing (I don't think there are serious contamination issues here!); possibly a sequence of such trips, to work out problems in extended space missions
2) Manned Venus orbiter + unmanned probes (obviously this is a big leap from (1), but I can't think of anything in between)
3) Manned Mars orbiter (landing on Phobos?)

It's true that Venus is subject to more radiation; but that also means more power available for the orbiter . Exposure to solar radiation would be a problem for any extended manned space mission anywhere. Venus' advantage is that the travel times would be shorter. I'm not an engineer, though, so I have no idea what the technical problems would be in not only sending a crew out and bringing them back; I imagine they are different from, but not more complex than, returning a crew from Mars.