By David Warmflash, MD | 15 July 2016
Genetic Literacy Project
DNA sequencing equipment will be operating soon in spaceflight. Following a similar path as computers, sequencing has evolved in the course of just a few decades from complex webs of inefficient machines filling rooms to hand-sized, user-friendly, automated devices that can do a lot more in less time time.
It’s a milestone, and so the 100-gram sequencer designed by the UK’s Oxford Nanopore that’s scheduled for launch on July 16 to the International Space Station (ISS) deserves all of the attention that it has been getting in tech savvy media like MIT’s Technology Review.
Now They’re Sequencing DNA in Outer Space https://t.co/MBPLnqNEIf
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The sequencer is smaller and lighter than most Earth-bound devices of equivalent capability and its uses in Earth orbit—and eventually on the Moon and on flights to Mars or asteroids—will be multifold. For instance, if an astronaut gets a urinary tract infection—something that actually happened to Apollo 13 astronaut Fred Haise coinciding with a spacecraft malfunction that nearly killed the crew of three—the sequencer could diagnose it and tell physicians which organisms it is. And the very same device could identify fungus or bacteria that could be growing in/on—and damaging—parts of the spacecraft.
The world of biotechnology also has great expectations that the device may help detect Martian microorganisms based on expectations that putative microbes native to the Red Planet would have DNA. But we can’t be so sure about this, and so the astrobiology benefit of the sequencer is more speculative compared with the benefits for the health of the astronauts and spacecraft.
Searching for Martian microorganisms has been tricky
Astrobiology conferences always include presentations of ingenious methods and instruments that robot landing craft and rovers could use to test the environment for native microorganisms. Some of the proposed methods have involved direct detection of the presence of DNA, or its components, in samples of Martian dirt. Other proposals have taken different approaches based on an assumption that Martian life would utilize DNA as genetic material, but thus far the only life detection tests performed on Mars took biochemical approaches that did not depend on Mars life having anything in common genetically with life on Earth. These were the three biology experiments carried to two locations on Mars by NASA’s Viking spacecraft in 1976.
The three Viking biology experiments asked fundamental questions about Martian dirt samples that a robot arm scooped into the instruments:
- Is there anything in the dirt that captures energy from light and uses the energy to make high energy food molecules from gases, like carbon dioxide (CO2) and carbon monoxide (CO)?
- Is there anything in the dirt that consumes high energy food molecules and releases waste as lower energy gasses (such as CO2)?
One of the three experiments seemed to provide a YES answer to the second question at both Viking landing sites, but in the 40 years since the mission we’ve been learning that the chemistry of the Martian dirt is rather complex. Consequently, the jury is still out on whether microorganisms native to Mars exist today at the planet’s surface, and if they do exist whether they had any influence on the Viking findings.
The three Viking biology experiments have been criticized for their limitations, most of which resulted from the need to conform to size, weight, and budgets of the early 1970s. The experiment that came out positive, for instance, could have been done in a slightly different way. Rather than consisting of a mixture of organic molecules, the test “snack” given to the Martian dirt could have been separated into into “left-handed” and “right-handed” molecules. This is what the investigators wanted to do originally, since life is known to be selective for chemical handedness. All life on Earth uses right handed sugars and left handed amino acids, so finding the same, or opposite preferences in Martian dirt would indicate the presence of life. Conversely, finding that Mars dirt reacted the same for a right-handed chemical and its left handed counterpart would suggest the response was due to the presence of reactive chemistry in the dirt, but not biology. Such an experiment almost flew to Mars in the 1990s on a Russian probe, but the probe did not reach Mars.
If Martian microbes exist, then detecting, amplifying, and sequencing their DNA would pick them up with higher sensitivity than any of the Viking tests of 40 years ago, but that’s assuming the organisms have DNA. This would be the case, if Mars life and Earth life are actually the same life, due to meteoroids carrying microbes between the planets. It’s also possible that DNA-based life emerged on Mars independently from Earth life, but it’s also possible that life emerged with something other than DNA to store and transmit genetic information. In the latter case, a high-tech take on the Viking biochemical approach to life detection could end up being more productive.
Reprinted with permission from the author.
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