----- Original Message -----
From: "Gary McMurtry" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, October 10, 2001 11:49 AM
Subject: Re: Looking for Europan DNA
>
> At the Flagstaff meeting of the Europa Focus Group, we discussed
> possible lander instruments. Since *yours truly* was present, there
> may have been a small bias toward a mass spectrometer. These
> instruments are versatile and have amazing sensitivity. The Red
> Group proposed a GC-MS (gas chromatograph-mass spectrometer); the
> Blue Group (including myself) proposed a multi-head MS with capillary
> electrophoresis option. It could also do "straight" MS in either
> "soft ionization" electrospray mode or "hard ionization" mode with a
> field ionizer. The CE-MS and "soft ionization" MS are capable of
> large organics detection, including DNA, if you use a small rotating
> field mass spectrometer. The "hard ionization" would be better at
> isotopic resolution of specific compounds. Both ionization
> techniques can detect inorganic molecules, such as dissolved salts
> and gases. Our present field prototype can detect at sub-ppb levels.
> We're currently building another one that can (in theory) detect at
> sub-ppt levels--we'll see. The first prototype consumes <8 watts
> when activated, but if there's an RTG on the lander, power should not
> be a big problem. We have to get the MS system volume and weight
> down a lot, but again, this is just a development issue. Can do,
> especially if funded.
>
> Other instruments on the wish list were:
> UV-Raman Spect.
> Geophone(s)
> Solid-state pH-Eh probes
> Camera-microscope (can't go there without a camera!)
> Thermal probe(s)
>
> There were a few others, but once again I'm away from my
> notes--sorry. The gist of the sampling is a clean and cleanable
> chamber must receive the meltwater/ice/brine so that multiple
> experiments can be conducted on the same samples, ala Viking (great
> program--wrong planet!). A modest corer/drill was envisioned.
Thanks for the information. (Ron Greeley is out of his office till the
11th, so I haven't yet been able to get any information out of him on the
meeting's conclusions.) Two comments:
(1) If I were designing this thing, I'd include considerably more than a
"modest" corer-drill. The current feeling is that the radiation-modified
(or, more accurately, radiation-hopelessly-fouled-up) layer is only a
fraction of a meter thick -- but Murphy's Law applies to the natural world
as well as to human artifacts, and with a mission that is as expensive and
takes as long to fly as a Europa Lander, I wouldn't feel secure with
anything less than a drill capable of penetrating 10 meters. (Honeybee
Robotics is currently designing just such a drill, since drilling that deep
is a high priority for the Comet Nucleus Sample Return mission.)
Alternatively, Frank Carsey's proposed "CryoScout" -- a tether-linked
Cryobot that descends just 100 meters or so from its soft lander, which he's
proposing as one of the 10 Mars Scout designs for which NASA has provided
study funding -- might well be the best way to go for the first Europa
lander, too. (Carsey made it clear to me that his mission to Mars'
permanent north polar cap would also be a trial run for a later Europa
mission.) As Chris Chyba points out, a Cryobot would be able to filter and
process a LOT more meltwater than any lander with a surface drill -- and,
given the possible scarcity of Europan microbial remains, the more meltwater
we look at the better.
(2) While a mass spectrometer is obviously a superb instrument for
analyzing organic compounds in detail, is it sensitive enough to the overall
quantity of biotic compounds if they exist only in tiny traces? Besides
JPL's notes in my earlier message on the supersensitivity of Raman and
fluorescence techniques, see Jeffrey Bada's proposed Mars Organics
Detector -- which would have flown on the 2003 Mars sample return lander
before its cancellation, and which is now proposed for David Paige's
"Artemis" Mars Scout small landers. It roasts ground-up Mars rock, sprays
the emitted vapors onto a cold finger to condense them, and then uses a dye
and fluorescent light source to detect amino acids and PAHs in quantities as
small as picomoles. Moreover, the improved design Bada is working on for
Artemis would be hooked up to a capillary electrophoresis system to allow
the chirality of the amino acids to be determined, although their chemical
analysis beyond that point would be limited. It might be very wise to
include both types of organic analyzers on the Europa lander, one to provide
detailed analysis of fairly plentiful ones, and one to at least confirm them
(and provide a less detailed analysis) if they exist only in very small
traces in the sample.
==
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