- 3971 - LIFE - how will we detect it on exoplanets? Is there life on Mars? Been part of science fiction dramas for decades. But, so far most of humanity’s forays into the Solar System seeking signs of life have returned only ambiguity.
---------------- 3971 - LIFE - how will we detect it on exoplanets?
- NASA’s
Viking 1 lander designed its suite of experiments to find any signs of life, or
biosignatures, on the Martian surface, returned a mix of positive and negative
results that summed to an indeterminate answer. Scientists found no signs of life, but
insufficient evidence to say there were no signs to be found.
-
- Scientists
have a new tool that might make sure future astrobiology experiments return
clearer answers about what they find, and what they don’t, wherever they look.
-
- A “Laser
Desorption Mass Spectrometer”, or LDMS device using a cutting analysis tool
first pioneered in the pharmaceutical industry uses a laser to ionize material
from the surface ice of Saturn’s moon Enceladus. The instrument can detect larger organic
compounds more advanced than any of the biosignature detecting tools currently
aboard NASA missions.
-
- The LDMS
device is really a combination of two pieces of equipment. There is the laser
system, which zaps samples of material on other worlds.
-
- Using
lasers for this purpose is not entirely novel. NASA’s Perseverance rover
carries a Laser Induced Breakdown Spectroscopy instrument that can zap rocks
from some distance away and looks for patterns in the light based on how
different geological elements absorb light or fluoresce.
-
- But the LDMS
instrument is a bit different. It is not
looking at light, it is looking at mass.
-
- When you
zap a bit of rock or ice with a laser, you move electrons around, giving the
particles in the resulting vapor an electric charge. This allows the instrument
to pull them inside using charged plates and guide them into the second part of
the instrument, an analyzer known as an “orbitrap”.
-
- An orbitrap
contains a central electrode that looks a bit like a football. The charged particles oscillate around the
football at speeds commensurate with their mass. Get their mass, and you know
their elemental composition. Scientists
can infer what the molecule is based on the speed at which it oscillates back
and forth across this electrode.
-
- An orbitrap
is not the only instrument that can analyze particle masses to determine
molecular makeup, but it is one of the most accurate. Some very different
molecules may possess very nearly the same mass, and , some instruments cannot tell them apart. But
the orbitrap has high enough resolution that you know exactly what the chemical
formula is.
-
- The
combined laser and orbitrap analyzer should be capable of detecting larger
organic molecules than existing instruments such as the “Sample Analysis at
Mars”, or SAM tool on NASA’s Curiosity rover. Instruments like the SAM work by
heating samples of soil until volatile compounds begin evaporating.
-
- That system
works well for organic compounds that easily become gas, such as methane but it
can’t detect larger organic compounds like peptides, which are chains of amino
acids.
-
- The LDMS
instrument can detect peptides, and while finding peptides on another world
wouldn’t be a sure sign of alien life, the more complex the organic molecule
you find, the less likely it is to have been created through an abiotic
process.
-
- NASA was
still planning on sending a lander mission to Europa, the Jovian moon which
scientists believe hosts a massive liquid water ocean beneath its icy crust.
It’s possible there’s some form of life in those depths, and if any of that
water made it to the surface of Europa, a lander sporting an LDMS instrument
could detect it.
-
- There was a
robotic arm that scooped ice from the surface of Europa. It dumped it into
their sample handling system and it delivered to us on plates. Then we hit the sample with our laser and we
get the chemical composition.
-
- But by 2017,
budget cuts led NASA to put the Europa lander concept on the back burner, and
Arevalo’s LDMS instrument is now a tool awaiting a new mission.
-
- Weighing
in at only eight kilograms, compared to the 40 kilograms of the SAM instrument
on Curiosity, the LDMS instrument could go anywhere, from Mars to Europa, to
Saturn’s moon Enceladus, another icy, ocean-hosting moon like Jupiter’s moon
Europa. Jut waiting for a rocket ride!
-
April 23, 2023 LIFE
- how will we detect it on
exoplanets? 3971
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--------------------- --- Sunday, April 23, 2023
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