[X] My Assistant

[centsworth_II]

...I worry we might be pushing at the boundaries.

If it helps, at this time I would have to say I think
serpentinization is a more realistic explaination for
the methane. But it is hard to ignore that evidence
for life will be looked for in the Phoenix data.
At this time, there is no strong evidence for life
on Mars. We should however be able to discuss how
to rule out -- or in -- what evidence does exist as it
comes in.

[centsworth_II]

...the range of metabolic rates in earth based animal life forms covers at least
7 orders of magnitude (from hibernating brine shrimp to hovering hummingbirds)...

And hibernating bacteria would have a rate next to zero.

[Tom Ames]

And hibernating bacteria would have a rate next to zero.

On earth fixed carbon is fairly cheap, and can be excreted without much cost. It's plausible that Martian bacterial analogs have optimized their ability to sequester fixed carbon, so that the average rate of atmospheric methane production is much less than it is on earth.

[Guest_AlexBlackwell_*]

If it helps, at this time I would have to say I think serpentinization is a more realistic explaination for the methane. But it is hard to ignore that evidence for life will be looked for in the Phoenix data.

I'm not sure what you mean by that last sentence but it's important to note that Phoenix is not designed as a life detection mission, unless "life" happens to walk in front of the cameras. In any event, one should bear in mind that while TEGA and RA are to be subjected to some heightened level of cleaning and dry heat treatment to reduce bioload, my understanding is that funding was never available for complete, Viking-level sterilization of the lander or its constituent parts. So any detection of "life" would face that not insubstantial hurdle.

[centsworth_II]

I'm not sure what you mean by that last sentence but it's important to note
that Phoenix is not designed as a life detection mission...

Just basing it on this quote I already posted from the Phoenix web site:
"...scientists will be able to determine ratios of various isotopes of hydrogen,
oxygen, carbon, and nitrogen, providing clues to origin of the volatile
molecules, and possibly, biological processes that occurred in the past."
http://phoenix.lpl.arizona.edu/science_tega.php

Although Phoenix is not designed to look for life, it will be interesting to see what
the isotope ratio data tells the researchers. I'm sure it will be far from conclusive
and there will be many questions raised for future missions to look into. Phoenix
will be gathering types of data that have never before been gathered on Mars
-- very exciting.

[brellis]

Although Phoenix is not designed to look for life, it will be interesting to see what
the isotope ratio data tells the researchers. I'm sure it will be far from conclusive
and there will be many questions raised for future missions to look into. Phoenix
will be gathering types of data that have never before been gathered on Mars
-- very exciting.

What will the data tell to the operators of current Mars missions? Can Phoenix data supply additional instructions to the MERs or the orbiters?

[centsworth_II]

Can Phoenix data supply additional instructions to the MERs or the orbiters?

Of course, the Phoenix data will be of great help in providing ground truth
for the orbiters. The predictions of the orbiter data concerning amount of ice,
and its closeness to the surface can be compared with what Phoenix finds.
This will make orbiter observations of other areas not visited by Phoenix more
meaningful.

I can't think of any way that Phoenix discoveries can affect the MER mission.
Come to think of it, is there any way that one MER has affected the mission of the other?
The data of all the missions of course compliments each other in advancing
our understanding of Mars.

[edstrick]

If Phoenix succeedes, it will cast MUCH light on the chemical reactions that occured in the Viking Biology Experiments. There clearly is *INTERESTING* chemistry in the "soils" that is not really hinted at by bulk minerology and elemental abundance information. Few people believe Gil Levin's special-pleading for biological interpretations of the experiment's results, but while the preferred explanation is abiotic chemistry, we only have "preferred models" of what the soils did under different experimental protocals. Phoenix is going to do more wet chemistry tests in the MECA (I think) instrument that will be powerfully diagnostic of soil components. Sample return would be far far better, but is far far in the future, compared with Phoenix's "real soon now".

[djellison]

I'm really looking forward to a ramp-up of info about the Phoenix payload before launch ( the typical Science briefing etc etc ) as I think some people - even people here - will be suprised just how much they've got going on in there.

Doug

[centsworth_II]

If Phoenix succeedes, it will cast MUCH light on the chemical reactions that occured in
the Viking Biology Experiments. There clearly is *INTERESTING* chemistry in the "soils" ...

I wonder how much the soil chemistry of the Phoenix site will have in common with with
the Viking sites. Does the presence of much water (even as ice) and less UV radiation
result in radically different chemistry, particularly of the so called super oxides?

[Guest_AlexBlackwell_*]

Just basing it on this quote I already posted from the Phoenix web site...

Thanks. I thought you were referring to Phoenix's goals in searching out paleohabitats but I wasn't sure. Of course, that's a whole different kettle of fish than looking for signs of extant life.

Although Phoenix is not designed to look for life, it will be interesting to see what
the isotope ratio data tells the researchers. I'm sure it will be far from conclusive
and there will be many questions raised for future missions to look into. Phoenix
will be gathering types of data that have never before been gathered on Mars
-- very exciting.

Although Phoenix, due to its lack of mobility, may not garner the same public attention as MER, it will indeed offer some very interesting science; in fact, the science portion of Phoenix's proposal was rated very high during the Mars Scout AO selection process. Assuming it succeeds, Phoenix will serve as a nice precursor for MSL.

This post has been edited by AlexBlackwell: May 16 2007, 12:37 AM

[JRehling]

On earth fixed carbon is fairly cheap, and can be excreted without much cost. It's plausible that Martian bacterial analogs have optimized their ability to sequester fixed carbon, so that the average rate of atmospheric methane production is much less than it is on earth.

Interesting comment. Reminds me of two factoids I recently encountered. Housecats have more concentrated urine than people, dogs, etc., because as desert natives, they try to conserve water. Snakes take this even further, excreting the same waste as a solid with no water loss. Life... adapts.

[edstrick]

"I wonder how much the soil chemistry of the Phoenix site will have in common with with the Viking sites"

Probably a lot in the top centimeter. Stuff in contact with the ice.. that's another story.

[centsworth_II]

I get the impression that many of the chemical characteristics of the
surface soil are a result of interactions with UV radiation. I wonder
how much less of an impact UV radiation has at the Phoenix site on
the chemistry of the surface. If not much, Phoenix may have the
best of both worlds: Studies of the surface that can be useful in further
understanding of results from other sites, like Viking, and studies of the
totally new environment of the icy subsurface.

[centsworth_II]

Housecats....Snakes.... Life... adapts.

Of course any thoughts of how life may have (theoretically) adapted
for life on today's Mars should probably be restricted to the tactics
of microbes, which in any case seem to be even more adaptable
than multicelled life forms.