Planetary Protection Workshop (Forward Contamination)

This is the second of three posts about the planetary protection workshop I attended at NASA Ames from March 24-26, 2015. The first is here.

Forward contamination, in the context of planetary protection, refers to the transport of microbes from Earth to Mars. The title of the workshop, and many talk titles refer to “human extraterrestrial missions,” but really, we’re talking about sending astronauts to Mars to walk on the surface of Mars, drill holes in Mars, scoop up dirt from Mars, and then returning the astronauts to Earth. There was almost no talk about human habitation on Mars. First things first, I suppose.

So, John Rummel kicked things off with a brief history of planetary protection. The gist of it is that, because we at some point deemed the moon devoid of life and uninhabitable, we didn’t think much about planetary protection until we started exploring Mars. In 1991, the stance on planetary protection was basically, “Viking didn’t find life on Mars, therefore no big deal, let’s go explore.” In 2000, gullies were found on Mars, suggesting the presence of water, leading to the Pingree Park Workshop in 2005, which addressed the question: Can we explore Mars without contaminating it?

(I did not know this, but I learned from Gerald (Jerry) Sanders that there is water on Mars in the atmosphere, in hydrated soil, in permafrost, in icy soils, in recurring slope linnea (hypothesized briny water), and in aquifers that are suspected to be >1km below the surface. So, there are defined “Special Regions” on Mars that are more likely than others to be able to support Earth life, and those are to be avoided or treated super-special so as to avoid forward contamination.)

The forward contamination discussions fall into two broad categories: superbugs and human-associate microbes. First, there are some superbugs that could hitch a ride on the surface of spacecraft and find a place to grow on Mars. These are more likely to find a home on Mars, but it’s worth discussing ways to remove them from surfaces. Second, human-associated microbes are far less-likely to do well on Mars, but the general consensus is that we cannot avoid contaminating Mars with them. There seemed to be a little bit of concern that they would interfere with the search for life (by providing false-positives,) but most people seemed familiar enough with evolution to agree that we are not likely to mistake something with a 99% 16S rDNA sequence identity to Staphylococcus aureus for Martian life.

Paulino-Lima isolated a strain of Geodermatophilus that is extremely resistant present-day Martian UV radiation with LD10 at least 33 times greater than Deinococcus radiodurans. Read all about it here. He described some experiments in a “Mars chamber” that’s been/being built in Brazil. Interestingly, Brazil has a long history of astrobiology, reviewed here. He suggested that a big knowledge gap that we need to address is that everything we know about radiation resistance comes from cultured isolates, and that we should be doing more environmental work. Several UV-exposure experiments (e.g., by Shuerger, Mancinelli, and Paulino-Lima) showed that dust can provide a very effective shield against UV radiation. Dust particle size, and depth of coverage both have significant effects.

Marcco Mancinelli from SETI gave the keynote on the second day, discussing some experiments in Mars-like places:

Terrestrial analogs of Mars include the dry valleys of Antarctica and the Atacama desert. University Valley is cold and dry, with not much organic carbon. -20 deg C seems to be the limit for microbial activity, even in cold and dry-adapted sandstone endolithic communities there. The Atacama desert is the oldest, continuously dry place on Earth (which was in the news for flooding the day after this talk!) There you find endolithic communities in these salt-pillar-looking things (halites). The surface of the rock blocks UV radiation, but is translucent enough to allow photosynthesis.

There are also “space environments” orbiting the Earth. ESA has the BIOPAN, which is a little laboratory attached to a Russian satellite and EXPOSE, a research platform attached to the outside of the ISS. We’ve actually been “throwing everything into space” since the 60s, and most everything dies instantaneously. Bacillus subtilis is the exception. On NASA’s Long Duration Exposure Facility (LDEF) B. subtilis spores were viable after a six-year stint in space. Mancinelli also showed that halophiles (like those living in halites) could survive space exposure for 2 years.

How well-suited is Mars for Earth life? Not very.

Andrew Schuerger gave us a (ranked) list of 17 biocidal factors on Mars, that I think is worth presenting in full.

  1. solar UV irradiation
  2. extreme dessiccation
  3. low pressure (1-4mbar)
  4. anoxic CO2 atmosphere
  5. extremely low temperatures (global average of -61 deg C)
  6. solar particle events
  7. galactic cosmic rays
  8. UV-glow discharges from blowing dust
  9. solar UV-induced oxidants
  10. globally distributed oxidizing soils
  11. extremely high salt levels in surface soils at some sites
  12. high concentration of heavy metals in soils
  13. likely acidic conditions in regolith (I had to look that one up)
  14. perchlorates in at least some soils (although people were constantly shouting about microbial perchlorate metabolism)
  15. lack of defined energy sources freeof UV irradiation
  16. no known source of available nitrogen or carbon
  17. no obvious redox couples for microbial metabolism

That sounds like a pretty nasty place to make a living. Schuerger was also frequently the voice of “well, duh.” For example, his simulations suggest that if you’re standing on Mars, and you want to sterilize a piece of equipment, then you can just expose it to the sun for a few minutes-hours and you’re going to nuke everything. He also showed a cool study where they took the Moon-1 planetary rover on a drive over pristine snow on Arctic sea ice. When they stopped to camp along the traverse, he took samples from the floor of the rover and from the snow surface at points 10m away from the rover (ahead, behind, upwind, downwind) and plated them. Inside the rover was really diverse, outside the rover was nothing. This seemed like an interesting example of a study where culturing methods might actually be more sensitive than molecular-based methods. Unless you believe that unculturable things are less likely to be dispersed than the things that grew on the rover plates, this approach does a nice job of avoiding the issues associated with low-biomass PCR-based studies. So, as the rover moved over the ice, it wasn’t spewing forth microbes (well, duh.)

I had dinner with Amy Ross (the geologist) one night, she talked a lot about geology and caving and answered a ton of questions about NASA bureaucracy. And then the next day, she gave a talk as the ARCHITECT OF HUMAN EXPLORATION SPACE SUITS. I don’t how you don’t bring that up at some point in the conversation! The most interesting single fact I learned about forward contamination is that space suits are leaky. The current Mark III spacesuit has 50 leakage paths. How big are the leaks? What is leaking out? We don’t know. Seriously. So, that’s a knowledge gap.

Thinking about forward contamination is really fun, but the primary concern for planetary protection is the reverse contamination. I’ll post about that next!

Experimental design for microbiome research in space.

Thanks to Project MERCCURI, I’ve been fortunate to develop a relationship with Sharmila Bhattacharya, a researcher at NASA Ames who is doing Drosophila research on the ISS. Her group is developing a “Fruit Fly Lab” for any researcher to run experiments on the ISS. She’s sending up her own experiments on several upcoming SpaceX flights, and when possible, she is providing me with samples of fly carcasses, dissected fly guts, and/or fly feces obtained from swabbing the interior of the enclosures. She is interested in (among other things) the affect of spaceflight on immune function. Dovetails nicely with my interest in microbiome research, right!?

So, the first experiment (HEARTFLIES) I got two groups of fly dissected guts, enclosure fecal swabs, and fly carcasses. I did 16S rDNA PCR sequencing from them and found a HUGE difference between the flies that went to the ISS and the flies that stayed on the ground. That was pretty exciting until I realized that the space fly gut microbiomes looked basically like regular old fly gut microbiomes and the ground fly microbiomes contained something like 99% of a single OTU of Lactobacillus.

As it turns out, the media for the ground flies dried up. The flies were very dehydrated (which affected their heart assays as well.) “Never fear,” they told me, “we are going to re-do those ground controls.” Huh? It’s been more than a month since the space flies were sent into space. A new batch of flies cannot be used asa control for those space flies. It doesn’t matter that they are the same genotype, maintained in the same conditions. They are a totally different population now with respect to their gut microbiomes.

For these ISS experiments, they always use this type of “asynchronous control.” Why? Because they cannot synchronously mimic on the ground the conditions that the flies are experiencing in space. Why not? Because ambient conditions on the ISS fluctuate and they don’t learn about those fluctuations on the ground until well after they’ve already occurred. Makes sense. So, in subsequent experiments, they have been running “best guess” synchronous ground controls in addition to their asynchronous controls.

Tomorrow, I’m finally going to get to tour her lab at NASA Ames. We’re going to chat about these kinds of issues. For one thing, flies can swap microbiomes, but not genotypes. Do their experimental enclosures separate the genotypes? I have no idea. We’ll see tomorrow. I wonder if anyone who has piggybacked on experiments in animals like this has any wisdom to share?

Workshop on Planetary Protection Knowledge Gaps for Human Extraterrestrial Missions (Intro)

I’m at a NASA Ames workshop this week. The goal is to have a discussion about planetary protection with respect to human spaceflight, in particular to Mars, mostly during a “sample and return” mission and a little bit about human habitation on Mars.

I’m tweeting with #planetaryprotection. There’s also live streaming here:

The broad goal of planetary protection is to make sure that we don’t contaminate the universe with our Earth stuff and vice versa, forward and reverse contamination, respectively. The first half of the first day was an exhaustive review of previous workshops on the subject. The reports are available here. James Johnson conducted an extensive literature review, which will soon be published in Advances in Space Research Special Issue: New Challenges for Planetary Protection, so keep an eye out for that. The Outer Space Treaty of 1967 was also brought up by many times. Apparently (according to Cassie Conley) if you can decipher the language, Article IX indicates that the “highest priority for planetary protection is to protect the Earth.” Of course, planetary protection was a concern during the Apollo missions to the moon, but the protections (especially with respect to reverse contamination) were pretty flimsy. They splashdown in the ocean, change into a new suit, hop into a helicopter, get paraded past hundreds of people, and then enter quarantine for 21 days.


At some point, it was decided that there was no life on the moon, so reverse contamination dropped off the radar. As far as forward contamination is concerned, well, there not just flags and golf balls, but also many, many bags of trash and human waste sitting on the surface of the moon right now.

The second half of the first day consisted of talks on the subject of Microbial and Human Health Monitoring. I’ll post about those later.