How do we protect planets from biological cross-contamination?
In Michael Crichton’s 1969
novel The Andromeda Strain, a deadly alien microbe hitches a
ride to Earth aboard a downed military satellite and scientists must race to
contain it.
While fictional, the plot explores a
very real and longstanding concern shared by NASA and world governments: that
spacefaring humans, or our robotic emissaries, may unwittingly contaminate
Earth with extraterrestrial life or else biologically pollute other planets we
visit.
It’s an old fear that’s taken on a
new relevance in the era of COVID-19, said Scott
Hubbard, an adjunct professor of aeronautics and astronautics at
Stanford University.
“I have heard from some colleagues
in the human spaceflight area that they can see how, in the current
environment, the general public could become more concerned about bringing back
some alien microbe, virus or contamination,” said Hubbard, who is also the
former director of NASA Ames and the first Mars program director.
Hubbard is a co-author of a new report published last month by the
National Academies of Sciences, Engineering and Medicine that reviews recent
findings and recommendations related to “planetary protection” or “planetary
quarantine” — the safeguarding of Earth and other worlds from biological
cross-contamination.
Here, Hubbard discusses the long
history of planetary protection, the dilemma posed by Elon Musk launching a
Tesla Roadster into space, and the precautions in place to guard against
contamination by NASA’s upcoming Mars Sample Return mission, which is scheduled
to kick off this summer with the launch of the space agency’s Perseverance Rover.
Concerns
about planetary protection date back to the earliest years of the Space Age.
Can you briefly explain what the term means?
Even before Sputnik, there were
scientific meetings that discussed the potential for space exploration to a)
carry earthly microbes to other worlds, thereby confusing or contaminating
future scientific investigations, or b) return alien life to Earth and thus
possibly threaten our own biosphere. The former issue is called “forward
contamination” and the latter is defined as “back or backward contamination.”
These concepts were codified in the Outer Space Treaty (OST) of 1967, which has
been signed by over 120 countries, including the U.S.
The
report notes that the “advent of new space activities and players in the exploration
and use of space” is raising new issues with regards to planetary protection
(PP). What are some examples of new developments and what challenges and
concerns do they raise?
This phrase refers primarily to
space entrepreneurs such as Elon Musk (SpaceX), who launched his own cherry red
Tesla Roadster to a Mars-like orbit around the sun aboard a Falcon Heavy
rocket. We need some way of knowing whether they are following appropriate PP
procedures.
It also captures emerging issues,
such as serious planning for human Mars missions, including Musk’s aspiration
to send people to the Red Planet by 2024. There’s also the advent and explosion
of smallsats or cubesats. In addition, some very challenging new science
missions with very complex planetary protection requirements such as Mars Sample Return and Europa Clipper to a
moon of Jupiter are underway. Finally, there are many more international players
than before who may not have experience with PP issues.
Can
you summarize the main findings and recommendations from this new report?
First, NASA and the world need to
seriously plan for emerging commercial/entrepreneurial space activities in deep
space. The complication is that NASA is a mission agency with huge PP expertise
but not a regulatory agency like the Federal Aviation Administration, which has
little PP knowledge but issues licenses for commercial launches.
Our committee concluded that the Outer
Space Treaty applied to both the government and the private sector, and that it
was very clear some entity in the U.S. government needed to “continually
authorize and supervise” private activities in space.
Next, with the probability of humans
landing on Mars ever more realistic, our reports recommend that NASA conduct
research to see if there can be a Martian “exploration zone” where humans can
land and contamination, if it occurs, would do no harm. Spacesuits can leak or
“blow out,” potentially releasing all manner of earthly microbes and
contaminating the surface for any future science missions.
Lastly, small spacecraft with the
potential to go to deep space are being developed at very low cost at both
universities and companies and we highlighted concern about whether these small
spacecraft will be overly burdened by the cost of PP requirements. Stanford
developed some of the very first smallsats, called cubesats.
What
are some examples of actions that can be taken to reduce the “bioburden” on
spacecraft?
Past missions with large budgets —
such as Viking I and II to Mars in the mid-1970s — were able to use heat to
sterilize whole spacecraft. That approach is not possible today for a variety
of reasons. However, combinations of chemical cleaning, heat sterilization,
applying reduction credit for time spent in the highly sterilizing space
radiation environment and clever mechanical systems have been shown to be
effective in meeting requirements.
Humans obviously cannot be cleaned
like robots, so much more attention to spacesuits, human habitats and using
robots as assistants is required.
What
are some actions that NASA can take to guard against accidental biological
contamination for its planned Martian Sample Return (MSR) mission?
To control forward contamination,
the hardware sent from Earth will be thoroughly cleaned. The tubes that will
contain the sample that are aboard Mars 2020 (Perseverance Rover) have been
baked at a high temperature.
To guard against back contamination,
there is a major effort to “break the chain of contact” between the returning
spacecraft and Mars rock samples. For example, autonomous sealing and
welding techniques to create three or four levels of containment are planned.
In my opinion, and that of the
science community, the chance that rocks from Mars that are millions of years
old will contain an active life form that could infect Earth is extremely
low. But, the samples returned by MSR will be quarantined and treated as
though they are the Ebola virus until proven safe.
As for humans, the Apollo astronauts
from the first few moon missions were quarantined to ensure they showed no
signs of illness. Once it was found that the moon did not pose a risk, the
quarantine was eliminated. Such a procedure will undoubtedly be followed for
humans returning from Mars.
This
report was completed before the current pandemic. Is there anything you or the
National Academies would have done differently if you were writing the report
today?
With respect to the science and
technology, I think we would have provided much the same report. However, we
wrote a small section suggesting that NASA and a recommended new advisory group
take a very proactive approach toward educating the public about the
extraordinary measures being taken to sequester the returned samples and
protect the public. In the COVID era, this section should be emphasized.
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