Bacteria species part of Curiosity baggage on Mars

Curiosity rover
Credit: NASA

( —When the Curiosity rover landed on Mars in 2012, there may have been dozens of microbial species, having withstood pre-launch spacecraft cleaning. This is the finding of a study titled "Identification and Survival of Isolates Collected from the Mars Rover, Curiosity." The scientists who worked on the study, from the University of Idaho, Jet Propulsion Lab at CalTech in Pasadena, Idaho State University, South Dakota School of Mines and Technology, and Colby College, presented their findings on Monday to the American Society for Microbiology meeting in Boston.

Reporting on this project, Nature News said their study is the first to examine the entire archive of microbes collected from Curiosity. The study is not only interesting for the number of strains identified but also for observations about their resistance. Results from the study can now provide details about the microbes that inhabit the surfaces of spacecraft after microbial reduction.

Nature News, commenting on the findings, referred to "a surprising number" resisting extreme temperatures and damage caused by ultraviolet-C radiation, the most potentially harmful type.

In their presentation abstract, the authors explained how organisms were collected during MSL's planetary protection implementation campaign. (MSL refers to the Mars Science Laboratory.). Isolates were identified and characterized using standard culturing and molecular techniques. Results showed 62% of the 377 organisms identified were related to members of the Bacillus genus while 31% belonged to non-spore-forming genera. Many isolates showed resistance to desiccation (78%), and UVC radiation and 94% of the isolates could grow in the presence of elevated salt conditions (≥10% NaCl) and 35% at low temperatures (4C), while 11% of isolates could survive under multiple extreme conditions.

Mars Science Laboratory Curiosity Rover Animation

The authors' comments reflect a concern among scientists over contamination, as they said that "this study will help gauge whether microorganisms from Earth pose a forward contamination risk that could impact future life detection and sample return missions. The overall outcome of this study will provide knowledge about the hardiest of organisms on the and could benefit the development of cleaning and sterilization technologies to prevent forward contamination."

A Scientific American article in 2011 also noted why scientists are concerned about cleanliness standards: "Adhering to cleanliness standards is a way to make sure the mission does not transport Earth life to Mars. Doing so preserves the ability to study that world in its natural state and also avoids contamination that would obscure an ability to find native life on that planet, if it exists."

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More information: via Nature

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May 21, 2014
lol...our sterilization techniques select for extremophiles!

May 21, 2014
This is good... Future probes will find life on mars one way or another. And one way or another, mars will eventually be terraformed. We cannot colonize without contaminating, and we do have to colonize. So we might just assume that contamination at this point in time is intentional.

I wonder if they found any bugs that wouldn't be the result of normal environmental contamination, but which might have increased chances of survival? This would signify intention.

May 21, 2014
Stupid, really stupid reporting. Can bacteria survive several months in vacuum? No, not even extremophiles. Can spores survive in vacuum? Yes, but they can be damaged or destroyed by ultraviolet (and other) radiation. This article instead gets it right:

The most important point though, is that the bacteria studied were removed from Curiosity during cleaning. Was the cleaning expected to be perfect? No. But if bacteria did get sent to Mars inside Curiosity protected from UV radiation they will almost certainly remain inside Curiosity for decades. Can and will cosmic rays kill any such bacteria? Sure. Remember, Mars has little atmosphere or magnetic field.

Anyway this report is important documentation which may be needed if Curiosity is destroyed catastrophically and then some subsequent mission detects DNA traces. There will be a list to compare to before concluding that life has been discovered on Mars.

May 21, 2014
We should be doing our best to get DNA going on other planets/moons. Normally we talk about a hedge against humanity snuffing out, but I'd say hedging for DNA would be more noble, wiser, and realistic.

May 21, 2014
bacterial spores ARE bacteria.I would also suggest you watch Cosmos (2014, Ep 11) which mentions the (currently) popular theory on why Earth has had life for ~3.5 Gy while for the first several Gigayears, it was subjected to collisions with asteroids and planetesimals which would have heated the surface of the Earth to sterilization temperatures for thousands of years at a time.Its roughly as likely for Curiosity to suffer from "catastrophic destruction" as it is to be stolen by aliens. This possibility is no justification for anything. As far as your other claim...there is a huge difference between "will radiation kill all spores from Curiosity?" & "can radiation...": of course it "can". Based on the way dust accumulates, and the way the wheels kick up debris, the "will" will take decades, and innoculation is possible. So far there doesn't seem anywhere these spores can go which could support their growth. We fear doing the same to Mars as we did to native Americans, as we should be.

May 21, 2014
bacterial spores ARE bacteria.

No. Bacterial spores and bacteria are two different forms of the same organism. When cleaning Curiosity, the goal was to remove as many bacteria as possible without forming spores. It isn't easy, but rocket science never is.

As for radiation, in space Curiosity was subject to a cosmic ray bombardment which would easily kill almost any living thing. Cosmic rays are very high speed atomic nuclei which create a shower of subatomic particles when they hit something. The particles don't go very far if they hit solid metal, but they then create very high energy gamma rays which can blow completely through something as small as Curiosity. (Neutrino detectors are placed a kilometer or three down in deep mines to avoid cosmic ray showers.) Could something survive the trip? Possibly. But DNA and RNA fragments and some proteins are much more likely.

Do I think that Curiosity is going to be destroyed by a meteor? Sure, but not in the near future.

May 22, 2014
A shortcoming is that it is cultivable isolates. That is a few percent of all bacteria, IIRC.

@TGO: "intentional". A conspiracy theory claimed without (or rather, against) evidence can be rejected without evidence.

@eachus: I haven't read the paper, but the Nature article suggest the samples were done during and after cleaning (and hopefully before, to give an unbiased sample). Spore-building bacteria will make such as they meet the cleaning procedures (stress from that and from lack of nutrients). And while they will eventually die as inactive, non-DNA repairing spores, many or most are spread from the chutes and shell and may not stay spores.

The life detection problem isn't from finding Earth bacteria, it seems to me. Divergence times can identify recent stowaways; trace fossils are inherently old. The problem is when they get into other experiments or add biosignatures in the environment (e.g methane and broken down organics).

May 22, 2014
@Z99: I haven't seen it, but it doesn't sound like it includes the latest astrobiology. Transpermia from Mars became popular when earlier pathways for emergence of life seemed to be unconstrained chemical evolution, with a lot of contingency and so taking time. Even more popular when it turned out that Mars formed in ~3-4 million years and Tellus in ~ 30 - 40 and then was hit by Theia to make Earth-Moon some 60 million years later.

However, we now know that chemical evolution was much more constrained. Submarine alkaline hydrothermal emergence produces almost-life cells which metabolizes CO2 and CH4 to 2C carbon compounds as soon as subduction starts in forming crust. [Russel et al, 2013.] And the Archean ocean (!) built the glycolysis and pentose phosphate pathways around these systems because Fe(II) constrains the chemical evolution of 2C compounds. ["Non-enzymatic glycolysis and pentose phosphate pathway-like reactions in a plausible Archean ocean", Keller et al, Mol Sys Biol 2014]

May 22, 2014

So we can predict trace fossils as soon as we have rocks that can have them, and that is what we see. Estimating transpermia rates makes it more likely life emerged locally IMO. [I posted one such estimate in a comment years ago; it can be googled, I hope.]

Moreover, contra Tyson, it looks like the late bombardment was survivable. When people started to actually model it, the crustal heating vs prokaryote spread makes it likely thermophiles survived without breaking a sweat. The latest paper even has the crust never reach 100 degC with the latest geophysical constraints, and that scenario is actually tested against the impact damage of found zircons (the first terrestrial evidence of the late bombardment)!

On the other hand, better understanding of the bombardment has added a likelihood of 1 ocean evaporator where there earlier were none. The subsurface crust was always habitable though. ["The impact environment of the Hadean Earth, Abramov et al, Chemie der Erde 2013]

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