NASA’s Planetary Protection Review Addresses Changing Reality of Space Exploration


Oct. 18, 2019

RELEASE 19-084

NASA’s Planetary Protection Review Addresses Changing Reality of Space Exploration

The bit carousel, which lies at the heart of Sample Caching System of NASA's Mars 2020 mission, is attached to the front end of the rover in the Spacecraft Assembly Facility's High Bay 1 at the Jet Propulsion Laboratory in Pasadena, California. The carousel contains all of the tools the coring drill uses to sample the Martian surface and is the gateway for the samples to move into the rover for assessment and processing. Credits: NASA
The bit carousel, which lies at the heart of Sample Caching System of NASA’s Mars 2020 mission, is attached to the front end of the rover in the Spacecraft Assembly Facility’s High Bay 1 at the Jet Propulsion Laboratory in Pasadena, California. The carousel contains all of the tools the coring drill uses to sample the Martian surface and is the gateway for the samples to move into the rover for assessment and processing. Credits: NASA

NASA released a report Friday with recommendations from the Planetary Protection Independent Review Board (PPIRB) the agency established in response to a recent National Academies of Sciences, Engineering, and Medicine report and a recommendation from the NASA Advisory Council.

With NASA, international, and commercial entities planning bold missions to explore our solar system and return samples to Earth, the context for planetary protection is rapidly changing. NASA established the PPIRB to conduct a thorough review of the agency’s policies.

Planetary protection establishes guidelines for missions to other solar system bodies so they are not harmfully contaminated for scientific purposes by Earth biology and Earth, in turn, is protected from harmful contamination from space.

The board’s report assesses a rapidly changing environment where more samples from other solar system bodies will be returned to Earth, commercial and international entities are discussing new kinds of solar system missions, and NASA’s Artemis program is planning human missions to the Moon and eventually to Mars.

The report discusses 34 findings, and 43 recommendations from the PPIRB, which was chaired by planetary scientist Alan Stern of the Southwest Research Institute to address future NASA missions and proposed missions by other nations and the private sector that include Mars sample return, robotic missions to other bodies, eventual human missions to Mars, and the exploration of ocean worlds in the outer solar system.

“The landscape for planetary protection is moving very fast. It’s exciting now that for the first time, many different players are able to contemplate missions of both commercial and scientific interest to bodies in our solar system,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate. “We want to be prepared in this new environment with thoughtful and practical policies that enable scientific discoveries and preserve the integrity of our planet and the places we’re visiting.”

The PPIRB, comprised of a high-level team of 12 experts and stakeholders from science, engineering and industry, examined how to update planetary protection policies and procedures in light of current capabilities. Such guidelines have periodically been updated and inform exploration by spacefaring nations that have signed the Outer Space Treaty since the 1960s.

“Planetary science and planetary protection techniques have both changed rapidly in recent years, and both will likely continue to evolve rapidly,” Stern said. “Planetary protection guidelines and practices need to be updated to reflect our new knowledge and new technologies, and the emergence of new entities planning missions across the solar system. There is global interest in this topic, and we also need to address how new players, for example in the commercial sector, can be integrated into planetary protection.”

NASA plans to begin a dialogue about the PPIRB report’s recommendations with stakeholders, and international and commercial partners to help build a new chapter for conducting planetary missions, and planetary protection policies and procedures.

For more information about Planetary Protection, visit:

To read the full report of the Planetary Protection Independent Review Board, visit:


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October 19, 2019 3:18 am

Gobsmaking diminishing returns.
Vested interests.
AGW bases on shonky science you want to check out the bull underpinning this new push for science troughers.
The USA is terminally insane.
So many important issues and Trump has gone the space wow shiny science object for electoral gain.
Madness abounds . . .

Reply to  Warren
October 19, 2019 10:09 am

Perhaps, perhaps not. We have yet to see the recommendations. I will not prima facie dismiss this endeavor.
It’s easy to lose focus during these tumultuous times of mis-information control, but keep reason in there.
Sometimes there is a baby still in the bath water.

Reply to  Rocketscientist
October 28, 2019 5:14 pm

“I will not prima facie dismiss this endeavor.” Then allow me. Because these stuffed shirt talking heads with no practical experience outside the lab can sit in their ivory towers and KNOW what may be harmful to that ball of rock (or ice or hydrocarbons or all of the above including none of the above) orbiting out beyond the Kuiper belts, and design a strategy that will absolutely protect it! See, they have failed already, and the thought experiment has only posited an inanimate inert lump, that has existed for billions of years already and still remains despite constant (in a relative sense) shellacking of galactic cosmic rays and meteors and what have you, and they don’t know. Their proposed “solutions” to this made up non-problem may be uniquely fatal and tragic in the most horrid Montague vs. Capulet tragedies of all Greek tragedies. Which all could have been avoided if they had simply done nothing! Now extrapolate your thought experiment out, take that mud ball, add an atmosphere, put it close enough to a source of energy that something could actually happen, and your infinite combinations of combinations has now been increased exponentially, infinity to the infinity, and Tribunal shall issue pronouncements that will Save The World!™ and apply equally to all the infinite worlds out there. And they have the balls to even think they might be right? Hell, they haven’t even figured out how to “Save” the one they inhabit, and I know they got it wrong on the one the inhabit, because the one they inhabit DOESN’T NEED SAVED!!! *sigh* When in the hell will they ever learn, or can somebody just force feed it, to just STFU?

October 19, 2019 3:25 am

The Andromeda Strain.

Joel O’Bryan
Reply to  Lancifer
October 19, 2019 4:47 am

about as likely as CAGW. Both make for good fiction though to scare people to handover their money and liberties.

Reply to  Joel O’Bryan
October 19, 2019 5:29 am

If you don’t believe other primitive life forms can exist , stop looking for them. If they may exist then will represent a threat totally unknown to any organism on Earth since life began.

European small pox eradicated something like 95% of the native population of S. Am by contamination to a totally strange pathogen. Why do you see this risk any differently ?

Orwell’s 1984 was fiction too, that did not stop it happening.

Joel O’Bryan
Reply to  Greg
October 19, 2019 5:51 am

Smallpox virus was highly adapted for human virulence long before it was introduced to a population with no herd immunity. So unless you believe native Americans weren’t humans…

And Your 1984 ref is a non sequitur.

Reply to  Joel O’Bryan
October 19, 2019 8:11 am

I agree Joel, this all sounds near preposterous. Any life outside the Earth isn’t going to be adapted to Earth/Earth life, and the chances of it running amok or even surviving are negligible. And solar-system debris/meteors are & have been falling onto Earth since it formed. Yes, most of the material burns up, but meteoric dust/small meteors make it to the ground constantly.

This is just another scaremongering meme — keep the populace alarmed/scared.

Reply to  Joel O’Bryan
October 19, 2019 8:56 am

…and your certainty is based upon what exactly?
BTW what exactly is this costing you? How does this negatively impact your life?

Let’s not find out the hard way. We may not get another chance.
We very well may find out that our biological systems are not all that different from those that exist elsewhere… because life may not have started here first.

Joe Crawford
Reply to  Joel O’Bryan
October 19, 2019 9:04 am

beng135 – You said: “… the chances of it running amok or even surviving are negligible.” When there is even the minutest (i.e., nonzero) probability of the total extension of life on Earth do you really want to neglect it.?

Reply to  Joel O’Bryan
October 19, 2019 9:42 am

Again, if it wasn’t noted, I remarked that debris is/has been falling on Earth all of its history, including debris from the Moon, Mars, Venus, Mercury, asteriods, etc, etc, etc. If there was any chance of some “Andromeda Strain” scenario, it would already have happened many times.

Reply to  Joel O’Bryan
October 19, 2019 11:46 am

JO: “about as likely as CAGW”

I’ve spent my life fixing mistakes caused by this sort of thinking. Risk mitigation is a reasonable concern when you’re travelling into the truely, completely unknown.

Reply to  Joel O’Bryan
October 19, 2019 11:54 am

this whole comment thread lends credence to the libs and Griff’s contention that the forum commenters are a bunch of cranky old men who just reject everything new and different.

Joel O'Bryan
Reply to  Joel O’Bryan
October 19, 2019 12:54 pm


I’m all for robotics and AI as a means to explore beyond Earth’s biosphere. It’s just all the baggage we have to take along to space to make it habitable for our fragile bodies. The needs for an extended stay beyond LEO makes it all a colossal waste when we can return >98% of that science with robotics/AI at 1/10th the cost. Which then allows us to do 10X robotics exploring as sending frail humans into space.

The only valid reason IMO to attempt any manned mission beyond LEO would be to interact on mission to an ET off world to prevent cross-contamination of our Earth and for the visitor with Earthly biota.

Pat Frank
Reply to  Joel O’Bryan
October 19, 2019 1:30 pm

I suspect the worry is more that Earth life will contaminate other planets, than that any possible life there will affect anything on Earth.

Contamination of other planets with Earth organisms (especially humans) is inevitable, of course.

But the early scientific work really needs to be free from, and careful about, artifactual discoveries that are actually successful transplants from Earth.

Possible life on other planets in this solar system may not share an identical genetic code. Did they not, infectious compatibility is unlikely. More likely is an allergic response to them.

But anything that is native to, say, Europa, will have developed in a spare environment, compared to the warm tumult of Earth.

Earth life to Europa life would be like tropical life vs subarctic life on Earth. The tropics are the source of diseases and competitive biodiversity.

Any life on Europa is likely to be steam-rolled by anything that arrives from Earth.

I believe the concern is to prevent that happening until at least a proper scientific inventory is taken.

Also, as soon as a group starts talking about “stakeholders” I grab my wallet. I want no NGOs in any negotiation, anywhere. Those people are irrational partisans, and incapable of dispassionate and fair analysis.

Pat Frank
Reply to  Joel O’Bryan
October 19, 2019 1:31 pm

because life may not have started here first.

It sure looks like it did. Or at least started here independently of anywhere else.

Pat Frank
Reply to  Joel O’Bryan
October 19, 2019 1:33 pm

Cube, “bunch of cranky old men

The argument of someone who doesn’t have an argument.

Reply to  Joel O’Bryan
October 19, 2019 8:50 am

Joel, you may or may not be correct regarding existence of extraterrestrial life forms, however you might want to reconsider your cavalier attitude.
Human experience has demonstrated that ill-considered contact with alien regions can have devastating impact to indigenous flora and fauna unfamiliar with new disease and invasive species – to both regions. While explorers introduced European viruses, bacteria and rats to the New World, they also brought back syphilis to Europe. This is some what excusable after the fact due to ignorance of germ theory, but we are not so ignorant any longer regarding biological contamination. However we may discover in the future that we have contaminated these “new worlds” in some other as of yet unknown factor.
We have routine border inspections for disease control, and it still gets through. Why do you think they ask those “silly” questions on entry visa applications and customs forms such as: “Did you travel to or visit agricultural facilities or handle live stock during your stay?” Because they want to know who likes animals? Why do you think we we establish quarantine zones? (BTW quarantine originally meant 14 days isolation)

Precaution should be a priority, there is no excuse for sloppiness, when we do know better.

Recently in previous posts, I lamented rather strongly regarding the Israeli’s reckless and ill-considered experiment that went awry badly and scattered tardigrades onto the surface of the Moon. Such biological contamination, while seemingly harmless could have huge impacts. If nothing else that area of the lunar surface will forever be suspect for any material collection samples due to the contamination.

Reply to  Rocketscientist
October 19, 2019 9:59 am

Rocketscientist, you are raising the Precautionary Principle!

Reply to  Retired_Engineer_Jim
October 19, 2019 6:22 pm

Not really, the ‘Precautionary Principle’ would dictate we not even explore in the first place.

In this regard, the precaution I suggest is not much more than you would expect from a competent surgeon.

Reply to  Rocketscientist
October 19, 2019 10:36 am

Meh. Contamination from other areas on the Earth isn’t remotely comparable to imagined contamination from outside the Earth.

Joel O'Bryan
Reply to  Rocketscientist
October 19, 2019 12:38 pm

It is reasonable to expect that extraterrestrial microbial-like life exists throughout our galaxy on exoplanets with liquid water and a stable star. The odds of it considering the vast number of opportunities and how quickly it appeared on Earth makes that a near certainty. But advanced life beyond microbes… that’s another story.

Microbial life in biofilms and mats of floating/attached cells was all there was on Earth for almost 3.5 Billion years, 77% of Earth’s history. This is what we expect to find when we search for evidence of exo-biology. The entire SETI effort of looking for EM/RF signals from an intelligent ET is wishful nonsense that provides a few people an income provided by other equally ignorant people. The Fermi Paradox tells us that.

Even in the past 500 million years there have been several close calls for Earth with near-100% sterilizing level events, even for microbial life. And the rise of complex organisms to include animal life with complex nervous systems depended on many factors of Earth’s stability and isolation from lethal events. One is 600 million year dearth of fully sterilizing events for Earth, events that appear with a near 10-100 million year stochasticy across the galaxy — such as nearby gamma ray-spewing supernovae, and has allowed a continued evolution to proceed to highly complex hierarchical social organizations by many individual copies — us and ants. Indeed, some level of “near-sterilizing, near total extinction-level” events may have been key to removing existing fauna structures to allow newer, faster evolving ones to quickly fill newly vacated ecological niches. A near sterilizing bullet to Earth was 66 million years ago and that so far has produced homo-sapiens with big brains, opposable thumb mobile digitized hands, and upright walking to free those hands to other tasks.

Microbial life probability though is vastly different from the probability of human-level cognition, communications, tool making, and concurrent abstract thinking development. Our own evidence here on Earth indicates microbial life quickly organized itself within a several hundred millions years after the end of heavy bombardment period 4.2 Gya. There is no reason to think this can’t/doesn’t occur through the galaxy on similar well-water endowed exo-planets where the stability of a unitary, “gentlemanly” star incubates life (but don’t look for it around brown dwarfs, they likely spew far too much coronal ejections and X-rays even though liquid water “habitable zones” seem to be present).
Could microbial life have evolved once on a warmer wet Mars? Maybe.
Or still exist in Europa’s brine ocean below a 100 km thick ice covering? Maybe.

Michael S. Kelly LS, BSA Ret.
Reply to  Rocketscientist
October 19, 2019 5:00 pm

In Return to Earth, Buzz Aldrin discusses the extended quarantine in the Lunar Receiving Lab at the Manned (now Johnson) Spaceflight Center.

“All of the precautions were explained to us so that we wouldn’t think that it was just a bunch of Mickey Mouse thinking, but whenever the opportunity arose, one or the other of us would poke fun at the NASA engineers who supervised the quarantine. They met their sealed-off Waterloo several days later when a stream of red ants appeared in the kitchen and proceeded to grow steadily in numbers. We happily kept them well informed about our visitors.”

Reply to  Rocketscientist
October 19, 2019 9:38 pm


Syphilis was spread to Europe, as smallpox and measles were spread to the Americas, via contact between contagious and uninfected individual of the same species – exactly the same DNA, metabolism, and so on.

Syphilis, in particular, was transmitted to Europeans through very intimate contact. There definitely needs to be a rule of “No sleeping with the blue-skinned natives, no matter HOW sexy they are.” (Ref: a truly horrible and stupid movie that I shall not name.)

That being said, returning samples do need to be strictly isolated until they have been analyzed to ensure that there is at least nothing more complex in them than unorganized amino and/or nucleic acids. Organized chains of either could possibly behave like prions, which are not alive, but will replicate in the body and eventually cause a very nasty death.

However… I think the question is rather moot on something nasty coming back to Earth. Why? Because proper practice will keep the samples from being contaminated by terrestrial material, which automatically prevents the reverse contamination.

There used to (may still) be a special number to call if a meteorite happens to land in your back yard. Coworker of mine whose husband worked with Dr. Shoemaker at the U of A gave me the card many years ago (sadly, disappeared in one of the two dozen or so wallet cleanings since then). On the back was a short list of what to do until the researchers showed up, which would be ASAP.

Reply to  Writing Observer
October 20, 2019 12:00 pm

I always though the Orion slave girls were more alluring.
…meh that’s what transporters are for, biological filtering/screening.

Reply to  Joel O’Bryan
October 19, 2019 11:45 am

JO: “about as likely as CAGW”

I’ve spent my life fixing mistakes caused by this sort of thinking. Risk mitigation is a reasonable concern when you’re travelling into the truely, completely unknown.

Joel O'Bryan
Reply to  Cube
October 19, 2019 12:45 pm

If Columbus had followed proper risk mitigation strategies, he’d have stayed in bed rather than risk a journey across an unknown ocean with barely ocean worthy vessels to find treasures of the Orient via a western route.

Reply to  Joel O'Bryan
October 20, 2019 12:07 pm

They followed the best risk mitigation procedures know to them at the time. That’s why they sent 3 ships, instead of only one. And rats on ships were a scourge for the ships as they ate and contaminated food stores. Failure to properly man the lines against incursion while at port was a serious offense. Obversely, when ships came in from foreign ports they were required often to wait off-shore at anchorage during quarantine.

Reply to  Lancifer
October 19, 2019 10:13 am

My initial thoughts as well, but the obverse it true also.

October 19, 2019 3:52 am

Trump wants to be the next president to talk to astronauts on the moon.

Joel O’Bryan
Reply to  Kevin
October 19, 2019 4:51 am

Seeing as how a US manned Lunar mission is at least 10 years away, your troll comment isn’t even a good effort at trolling.

Reply to  Joel O’Bryan
October 19, 2019 5:32 am

I don’t think that Elon is that patient. His Starship/BFR project is already in prototype assembly. Further, the engines have already been on flight tests, which is pretty amazing given its revolutionary design and fuel choice.

Joel O’Bryan
Reply to  Patrick
October 19, 2019 5:56 am

He needs NASA US government approval for even a manned suborbital flight. Which is yet to occur. Then LEO orbital flights need flight hardware not tested yet. Years away. Then Lunar capable hardware that is still on the drawing board.

Elon going to find himself out of cash for these private ventures before he gets much further. Bezos has a much better chance as he actually has gobs of cash to burn.

Reply to  Joel O’Bryan
October 19, 2019 7:11 am

Can’t wait to see the environmental impact statement for space launches. Unless we hold the Democrats and global-warmers at bay, future books on space exploration may say something like, “Man has consigned himself to planet Earth to protect its environment from the CO2 and carbon soot produced by lauching spacecraft into orbit.”

Reply to  Joel O’Bryan
October 19, 2019 9:26 am

The environmental impacts are already controlled, however they are mostly concerning spillage/loss of toxic fuels (some are nasty), flotsam and jetsam. Populations that get overflown during launches take a dim view of ejected items or ice chunks crashing through their roofs. We handle most of this by launching over the oceans (which is why Arizona space ports are at an extreme disadvantage), I’ll assume you know why most flights launch eastward.
The rocket plumes themselves can be absolutely benign if LOX/LH2 is the choice, or more sooty if LOX/CH4 is the choice , although almost all propellant combinations will be O2 rich because oxygen has a lot of mass and these are after all mere impulse engines.

Reply to  Patrick
October 19, 2019 6:29 am

Starship, no – I think its a B-Ark! to save the population from the mutant star goat!

Doug Huffman
October 19, 2019 3:57 am

Space exploration will be too expensive for exploring the blackhole of welfare.

Joel O’Bryan
October 19, 2019 4:42 am

The reality is no matter amount effort to clean space vehicle/planetary probe, there is going to be substantial Earth (terrestrial) organisms (forward contamination) introduced to wherever we go.
Past policies from the Viking Lander era were too demanding, restrictive, and burdensome. For a manned Mars mission not “contaminating” Mars surface with Earth organisms would of course be impossible as even astronaut surface EV suits would be put on by astronauts physically handling the exterior surfaces of the suit that subsequently goes “outside” to come in contact with Mars in situ soil and atmosphere. Shedding terrestrial biota would be then unavoidable no matter what level of effort prevent it was undertaken. (personally I don’t believe a manned Mars mission will happen, as it’s a suicide mission with current propulsion technology due to the extended radiation environment exposure risks.)
But even at the purely robotic (unmanned) mission level, such cleanliness criteria is unachievable. For all the Mars surface missions delivered there, no one believes that we haven’t delivered Earth microorganisms to the surface intact. And stopping robotic drilling operations on Mars or Europa landers for fear of contamination is ridiculous if we want to learn more with these many multi-billion dollar missions.
The likelihood terrestrial organisms remained viable after a many months long transit in the radiation and cold, hard vacuum of space to reach Mars (or Huygens lander at Titan) is debatable though. We know at some level spores might survive, and even tardigrades are pretty hardy little buggers.
Eventually as it becomes more likely that low cost CubeSats will be put in low Mars orbit, more Earthly contaminated debris will be delivered to Mars surface. We should just accept that fact. If we ever do find evidence of fossilized Martian life it will clearly be billions of years old to an era when liquid water flowed on Mars surface. This sort like the quantum uncertainty. Measuring it with in situ instruments from Earth will always have the unknown risk of contamination. Just get over it. You can’t have you cake and eat it too.

Reply to  Joel O’Bryan
October 19, 2019 5:41 am

Project Orion is well within our grasp technologically, and could do a round trip within a week or two. Environmentalists would lose their minds though, even if launched from LEO.

John McClure
Reply to  Patrick
October 19, 2019 6:48 am

You forgot the /sarc.

“Project Orion was a study of a spacecraft intended to be directly propelled by a series of explosions of atomic bombs behind the craft (nuclear pulse propulsion).”

John McClure
Reply to  Joel O’Bryan
October 19, 2019 6:42 am

What? Bacteria and viruses can survive in the vacuum of space?

What? Robotic trips to neighboring solar systems?

Reply to  Joel O’Bryan
October 19, 2019 8:38 am

Joel — quite right. The contamination meme is ridiculous. And very doubtful any Earth-life is going to survive outside Earth (and vice-versa). This seems like just another extension of the current cultural psychosis.

Just my opinion, but the moon, asteroids, other planets & their moons are out there for us to explore, use, mine, colonize, terraform — within reason. But I don’t think any of that other than simple exploration is going to happen anytime soon — way too difficult & expensive.

October 19, 2019 5:18 am

Wow. Somebody has too much money.

October 19, 2019 7:06 am

If only NASA were putting as much effort into getting to other worlds, this might serve some purpose. Like so many areas of government, they’ve discovered they can make proclamations like this, without doing any actual work.

Remember, NASA doesn’t send things or people to space, NASA asks the lowest bidder to send things or people too space. And with the announced Boeing/SLS contract, they’ll actually pay high bidders to, truthfully, send nothing at all to space, not even test launches.

Joel O’Bryan
Reply to  Max
October 19, 2019 8:22 am

NASA’s manned space flight programs are make-work Yobs Programs for engineers and managers.

October 19, 2019 7:07 am

We need to protect Earth from impacts small and large:

Hocus Locus
Reply to  Walter J Horsting
October 19, 2019 8:20 am

YES… when is NASA (and the military, fer gosh sake) going to implement a credible Planetary Protection Policy to protect the Earth from slate-wiping asteroid and comet ‘contamination’?? I could use some help convincing them.

J Mac
Reply to  Walter J Horsting
October 19, 2019 3:55 pm

When I read the ‘headline’ for this article, I thought I would be reading about a dedicated program to not only identify earth approaching asteroids, meteors, comets, and alien space ships };>) but also intercept them at sufficient distance to redirect them away from earth with available and developmental technology. Instead, I read a story about the impending disaster of a mutant flu virus destroying Mars! Sheesh….

Tom Abbott
October 19, 2019 7:32 am

From the article: “It’s exciting now that for the first time, many different players are able to contemplate missions of both commercial and scientific interest to bodies in our solar system,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate.”

This *is* exciting. We’ve been waiting a long time to get to this point.

Soon there will be a breakout of humans into space. The next couple of decades are going to see a big change. Free enterprise will drive space development in orbit, as it is doing today with launch vehicle development.

Assuming there is free access to space. That’s not been guaranteed.

J Mac
Reply to  Tom Abbott
October 19, 2019 5:14 pm

I sincerely hope you are truly prescient on this topic, Tom!

October 19, 2019 8:07 am

No littering. They will have to establish the limits of purity within current technology if spacecraft are to go and return without damage.

October 19, 2019 8:38 am

The universe is 14 billion years old.

In that time do we really think life has only happened once on this particular planet?

Life must have existed out there and will exist out there when all life on earth is gone.

The chances of life existing on more than one planet at once is possible.

The chances of more than one intelligent species capable of interstellar travel appearing at the same time, not so much.

October 19, 2019 9:03 am

It would seem that a far more important Planetary Protection plan would be protection from the existencial threat of a major asteroid strike.

Reply to  E.Martin
October 19, 2019 9:44 am

The NASA has the Dart project which is tasked with
building a system to intercept a threatening asteroid.

October 19, 2019 10:09 am

We don’t know what we don’t know. Sure, don’t expect a highly tuned molecular pathogen like a virus miraculously able to take advantage of our cellular machinery. However, another critter might just want raw materials from us – an autotroph. Doesn’t care about how we are put together, just wants what we are made of.

Of course, that’s all highly unlikely, but we don’t know what threats exist. Put a lab on the Moon. Do preliminary sample return work there. Try to prevent contamination. Maybe see what happens when samples are exposed to terrestrial conditions.

Meanwhile, we need to live where we go. And we will bring our own critters with us. The Star Trek fantasy of DNA for all living things is silly beyond words. There will be other forms of life with other biochemistries that match the elemental abundances of the home world, and function under the physico-chemical conditions present. When we finally meet them, we will be amazed. When we finally figure out how they live, we will nod and say that makes sense, not so difficult to understand. But there is a long way to go between now and then.

When we do “contaminate” another world, it will be a good thing. Both forms of life will coexist and develop in unpredictable ways, as Nature has always worked. Think about what happens over 1 billion years. Humans still around? Not a chance. Our progeny? Maybe. More interestingly, what happens on the worlds where two biochemistries can interact, and develop new forms impossible without each other. We will have made that possible. They may one day wonder if traces of two different biochemistries meant two different types of organisms co-evolved and perhaps merged. And if so, where did they originate? Both on the same world? They may never know the answer.

And it won’t matter.

October 19, 2019 1:48 pm

So some here believe there’s ET life.
Could we see the evidence for that?
Anyone . . .

Reply to  Warren
October 19, 2019 2:07 pm

Direct evidence? No.

But as Carl Sagan said, we live around an ordinary star in an ordinary galaxy. In a universe of billions of galaxies, with untold number of stars, and an even greater number of planets. That life on earth is unique is mathematically unlikely. With our understanding of the origins of life here, it should have happened many times elsewhere as well.

We are not special.

Joel O'Bryan
Reply to  Warren
October 19, 2019 3:09 pm

Could we see evidence for that?

Yes, it’s us.

2 lines of evidence combining with probability and deep time.

1. Direct evidence that microbial life started pretty quickly here after the Earth’s environment stabilized (heavy bombardment ended). Environmental conditions were pretty harsh for at least 2 Gy by today’s standards (no oxygen, a reducing atmosphere of methane and CO2 and maybe ammonia) yet that life continued (obviously) to evolve ever-more molecular complexity.

2. Astronomy observations. There are certainly vast number of exo-planets within a water-stable, habitable temperature zones spread across the hundreds of billions of star systems in the vastness of our galaxy. Lower probabilities of observed higher metallicity and yet being in a quiet backwater still provides many hundreds of millions of opportunities for exo-planets with a liquid water range and a well-behaved unitary star for warmth/energy but not too much.

1+2 –> So, probability –>. Microbial-like life.

But given that we know it took over 3 billion years of external stability for Earth to acquire something more complex than single-cell algae to evolve, anything more than microbial life forms and then the probability starts to act against that formation of higher level of complexity (multi-cellular animals and plants). Then sentient beings are another whole many-levels of improbability too unknown to even guess at.

– All the things we understand that kept Earth from becoming a Mars stripped of its atmosphere and cold and liquid waterless wasteland after a billion years of going around the sun (a geomagnetic dynamo that has operated for 3+ Gy) or,
– a Venus with a wacky rotation (an unlikely moon with lunar stabilization of Earth’s obliquity).
– The gravitational resonance of little sister Saturn that kept her big brother Jupiter from rampaging inwards to eject the rocky planets inside the frost line out to the depths of the Oort Cloud.
-Copious amounts of water delivery during the cometary bombardment period.
-Not too many big asteroid/comet hits (or substantially beyond the size of the Chicxulub bolide.)
-No nearby sterilizing supervnovae/kilonovae for at least the that last 600 Mya (we’ve apparently had a few close calls, but none so close as to be totally sterilizing, which is surprising given what we know today. That tells us we’ve likely been in a “quiet neighborhood” off the spiral arm of our galaxy.)

Reply to  Joel O'Bryan
October 20, 2019 8:34 am

Joel, thanks for your insights. We might be a one-a-galaxy situation.

David L. Hagen
October 19, 2019 2:25 pm

Planetary threat: Asteroid Impact
The far greater danger is a major asteroid impact on earth.
Rocks at Asteroid Impact Site Record First Day of Dinosaur Extinction
“When the asteroid that wiped out the dinosaurs slammed into the planet, the impact set wildfires, triggered tsunamis and blasted so much sulfur into the atmosphere that it blocked the sun, which caused the global cooling that ultimately doomed the dinos.”

Johann Wundersamer
October 28, 2019 2:00 pm

“The board’s report assesses a rapidly changing environment where more samples from other solar system bodies will be returned to Earth, commercial and international entities are discussing new kinds of solar system missions, and NASA’s Artemis program is planning human missions to the Moon and eventually to Mars.”

How much radiation hits the Moon?

“On Earth, the contribution to the annual terrestrial dose of natural ionizing radiation of 2.4 mSv by cosmic radiation is about 1/6, whereas the annual exposure caused by GCR on the lunar surface is roughly 380 mSv (solar minimum) and 110 mSv (solar maximum).”

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