Humanity Lights a Fire on Mars and the Implications for Life on Mars
The Fire on Mars and Kerogen
I was reading through the paper in Science recently, about
the discovery of organic matter in Gale Crater on Mars, by the Curiosity Rover
(Organic matter preserved in 3-billion-year-old
mudstones at Gale crater), Mars, when I came across the following interesting
passage:
Immediately preceding the 750°C peak set is a notable O2
release from sulfate decomposition (3), with
an increase in CO2 (Fig. 1E) suggesting that combustion limited to the most
ignitable volatiles (12) occurred in parallel with pyrolysis. It is also
possible that portions of the CO2 and CO (Fig. 2A) were derived from the
decarboxylation (2, 3) and decarbonylation of larger organic compounds, which
have been observed for Murchison macromolecular isolates (15). The same three peaks
are present but less discernable in Confidence Hills data, where the 750°C O2
peak is lower, suggesting that combustion was less influential on hydrocarbon
evolution (fig. S1 and S2).
So, we lit a fire on Mars.
I don’t recall any of the reports in the media noting this, or if they
did, it was downplayed. A bit of burying
the lede, in my opinion. After all, one
of the first things human beings do, and probably always did, in any new land
that they explore, is to start a fire.
So, this “Martian fire” strikes me as quite symbolic. Sure, it was a fire confined to a glorified test
tube, but still…
As the graph shows, there was a fairly sudden release of
oxygen from the pyrolysis of the sample (i.e. heating of the instrument, via
energy from a radioactive source on the probe), once the temperature reached
about 700 C. That was followed by CO2,
which peaked a bit later in the experimental run. So, it looks like a short, small blaze might
have occurred. At any rate, a fairly rapid oxidation.
The idea behind the experiment was to sample a 3 billion
year old Martian mudstone, located in the Gale Crater, then heat it up and test
the resulting by-products, with a particular focus on whether and how much of
the compounds detected were organic, in the sense of organic chemistry (i.e.
carbon based molecules).
There was some precedent for believing that there would be
organics – hints of this came from earlier work by Curiosity, as well as Martian
meteorites that had fallen on Earth.
At any rate, quite a rich soup of organic molecules were
detected by the mass spectrometer.
Again, quoting the paper (note that the reference to Mojave and
Confidence Hills are sites on Mars):
The diversity, composition, and
temperatures of coevolving volatiles observed in the Mojave and Confidence
Hills analyses above 500°C are consistent with the pyrolysis of geologically
refractory organic macromolecules that are typically found in carbonaceous
chondrites (14, 15), kerogens (17), and coals (18,
19).
Note that kerogen is a general term for a mixture of solid
organics in sedimentary rocks on Earth (it is a coined word that translates
from Greek as “wax birth”). On Earth,
kerogen is thought to be a by-product of living things, and can eventually turn
into petroleum, natural gas or coal.
That said, it is known that kerogen-like matter can come from
non-living sources (e.g. it can be found in interstellar clouds and carbonaceous
chondrite meteorites). We obviously don’t
know the source of the Martian material.
The paper notes that biological, geological or meteoritic sources are
all possible.
The Connection to the Viking Experiments
The Viking lander experiments of the 1970’s showed
tantalizing indications of life, in the Labelled Release results. These tests “fed” a rich nutrient mixture to
some Martian soil, and then looked for radioactive traced CO2 gas, that would be
released by life forms in the soil, if they were metabolizing the nutrient
mixture. The experiments did show such a
result, and they were consistent with results tested on Earth soils in which
bacteria could be found. However, the
life explanation was mostly abandoned in favor of non-biological chemistry.
One of the main refutations of the “it’s life”
interpretation of the Labelled Release experiment was that another Viking
experiment that was designed to look for organic matter, failed to find any. However as a 2016 paper by two of the Viking
scientists states:
“Lack of biologically relevant
organic molecules on the surface of Mars has also been considered a major
detriment to extant life. Recent reports
of complex organics, possibly of biological importance, are encouraging, although
analyses are ongoing and details are not yet available.”
The 2018 results from Curiosity certainly should bolster the
case for Viking’s apparent discovery of life in the Labelled Release
experiment.
The Connection to Science Fiction
An interesting connection to Science Fiction comes from an
old 1960’s movie called “Robinson Crusoe on Mars”. In that movie, a stranded astronaut derives
oxygen from heating oxygen-bearing rocks.
So, it is interesting that there is a bit to this idea, as far as we can
tell from the Curiosity results. Here’s
a scene of the stranded astronaut filling his oxygen bottles (and, yes, he has a monkey).
The movie was filmed before much was known about Mars, even
before the first NASA spacecraft did a flyby of the planet. The movie was from 1964, and the first Mars
probe flyby was in 1965. It is a
surprisingly good movie, for the most part, though the last part is a stretch. It is well worth a viewing.
Sources:
- Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars. Buch and Patrice Coll, Joel A. Hurowitz, John P. Grotzinger, Sanjeev Gupta, Doug W. Ming, Dawn Y. Sumner, Cyril Szopa, Charles Malespin, Arnaud, Brad Sutter, Amy C. McAdam, Heather B. Franz, Daniel P. Glavin, Paul D. Archer Jr., Paul R. Mahaffy, Pamela G. Conrad, Jennifer L. Eigenbrode, Roger E. Summons, Andrew Steele, Caroline Freissinet, Maëva Millan, Rafael Navarro-González DOI: 10.1126/science.aas9185 Science 360 (6393), 1096-1101.
- The Case for Extant Life on Mars and Its Possible Detection by the Viking Labeled Release Experiment. Gilber V. Levin and Patricia Ann Straat
- Wikipedia (Kerogen, Mariner 4 Mars Probe, Robinson Crusoe on Mars, Viking Probe)
- Google Images
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And now that you have read about some real cutting-edge
science, you should think about reading some Science Fiction (because all work
and no play can make you a dull person, or so they say). Here’s a novel that features a neutron star
(and a pretty girl, who is also an engineer, among other characters). The second book in the series features a
lunar near-catastrophe and some science about Lagrange points:
The Witches' Stones, Book 1 - Rescue from the Planet of the Amartos
Young Earth woman and spaceship mechanic, Sarah Mackenzie,
has unwittingly triggered a vast source of energy, the Witches' Stones, via her
psychic abilities, of which she was unaware. She becomes the focal point of a
desperate contest between the authoritarian galactic power, known as The
Organization, and the democratic Earth-based galactic power, known as The
Terran Confederation. The Organization wants to capture her, and utilize her
powers to create a super-weapon; the Terra Confederation wants to prevent that
at all costs. The mysterious psychic aliens, the Witches of Kordea also become
involved, as they see her as a possible threat, or a possible ally, for the
safety of their own world.
A small but fast scout-ship, with its pilot and an agent of
the Terra Confederation, Coryn Leigh, are sent to rescue her from a distant
planet at the very edge of the galaxy, near space claimed by The
Organization. Battles, physical and mental, whirl around the young woman,
as the agent and pilot strive at all costs to keep her from the clutches of the
Organization.
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