National Aeronautics and Space AdministrationThe Safety of Mars Sample Return
Planetary Protection is the discipline of
protecting solar system bodies such as planets
and moons from possible contamination by
Earth life, and protecting Earth’s biosphere
from any potential adverse effects that could
result from bringing material collected from
these bodies back to our planet.
The Mars Sample Return (MSR) program
being planned by NASA and the European
Space Agency (ESA) would pick up the
geologic and atmospheric samples being
gathered by NASA’s Perseverance Mars rover
and return them to Earth in the early 2030s.
The NASA-ESA team is working closely
with each agency’s planetary protection
leadership to ensure that every spacecraft
sent to the Red Planet has been cleaned to
prevent Earth organisms from compromising
scientifc investigations, and to implement
numerous steps designed to protect Earth and
provide safety assurance by preventing any
uncontained, unsterilized Mars material from
being delivered to Earth.
Assessing the Risks
The question of whether samples from Mars
could present a hazard to Earth’s biosphere
has been studied by several different panels
of scientifc experts from the United States
and elsewhere over the past several decades.
The reports from these panels have found an
extremely low likelihood that samples collected
from areas on Mars like those being explored
by Perseverance could possibly contain a
biological hazard to our biosphere.
Multiple different sources of scientifc evidence
contribute to this assessment. The evidence
includes the absence of any observed harm
to Earth’s environment from Martian rocks that
frequently fall to Earth in the form of meteorites,
and the fact that the Mars samples being
gathered by NASA’s Perseverance Mars rover
are from the frst few inches of a planetary
surface that is very dry and highly irradiated
naturally by the Sun, which would sterilize
all known active biology. (This is part of why
NASA’s science strategy is focused on fnding
traces of ancient life from long ago, when the
Martian environment was wetter and warmer,
and not modern life in these harsh conditions).
A Conservative Engineering Approach
Protecting the public, the NASA workforce,
and the environment from potential harm is an
integral feature of every agency program and
technology development activity. For MSR,
the most direct means of protecting Earth’s
biosphere is to securely contain all unsterilized
Mars material returned to Earth, using a multi-
layered approach involving a “container within a
container.”
The standards for safety engineering and
containment being implemented for MSR
are derived from “safety frst” industries such
as medicine and aviation. NASA and ESA
engineers are focused on designing and
delivering a multi-layered containment system
capable of bringing Mars samples to Earth
safely. The planned approach would provide
higher levels of isolation than anything achieved
previously in space fight, including for the
samples of lunar rocks, comet dust, asteroids,
and the solar wind successfully captured
and returned to Earth by earlier NASA and
international missions.
NASA Facts
Breaking the Chain with Mars
Collectively, these containment engineering and
verifcation activities are known as “breaking the
chain” of contact with Mars. These processes
would include steps taken at every stage of
the campaign: on the surface of Mars, in orbit
around the Red Planet, in fight between planets, and all
the way to the surface of Earth. Each step sequentially
reduces the potential that any unsterilized Mars material
could be released into Earth’s biosphere. Many of the
planned protective measures provide layers of redundancy
throughout the mission, and would enable safe sample
return under a variety of mission conditions.
The process begins on the surface of Mars, where the
Orbiting Sample (OS) container is protected from Martian
dust by an enclosure that is opened only to insert sample
tubes, minimizing the amount of dust that is allowed to
accumulate on the OS. Once launched into orbit by the
planned Mars Ascent System, the volleyball-sized OS
would be collected inside the Capture, Containment and
Return System (CCRS), a payload on ESA’s Earth Return
Orbiter.
As its name suggests, the CCRS frst captures the OS and
then seals it inside the frst of two containment vessels,
while simultaneously heat sterilizing any Mars dust that
might remain in the seam of this primary containment
vessel. The sterilization process would be done at a
temperature high enough to destroy protein structures
and inactivate any biological material in the small amount
of dust that might remain in the joint. Then, the sealed
container would be passed into a clean chamber inside
the CCRS that has been protected from Mars dust, where
it would be sealed inside a secondary containment vessel,
which would be then secured within a robustly designed
Earth Entry System (EES).
Other elements of breaking the chain include ejecting
much of the CCRS hardware from the Earth Return
Orbiter before it leaves Mars orbit, and using a
micrometeoroid shield to protect the EES during its return
trip to Earth aboard the orbiter.
The conceptual design of the Earth Entry System (EES) for Mars Sample Return includes redundant layers of
containment for the samples and a design that softens the effects of landing without a parachute.
National Aeronautics and Space Administration
Special Care Before, During, and After Landing
The trajectory of the return orbiter carrying the EES would
be pointed away from Earth until a few days before the
planned landing, allowing a fnal decision to be made
about proceeding with Earth entry using all available
information collected during the entire mission.
The EES is built to tolerate extreme conditions: it would
enter the Earth’s atmosphere at nearly 27,000 mph,
experience forces nearly 125 times greater than gravity
while slowing to just 90 mph, and land using only the
ground as its cushion. The cone-shaped vehicle and its
components, such as the “container within a container”
surrounding the OS, are being robustly designed and
tested on Earth to demonstrate their ability to withstand
forces well beyond those that would be experienced
during entry and landing.
Out of an abundance caution, the entry system and
its samples would be treated with the highest level of
care once having landed, as if they could be hazardous
biological materials. The EES will be quickly enclosed
in additional layers of containment, using procedures
based upon the proven principles and techniques used
by hazardous material response teams, and will be
maintained through transport to a dedicated Mars sample
receiving facility.
Such a Mars sample receiving facility would have design
and sample handling requirements equivalent to those of
biological safety laboratories used for research studies of
infectious diseases. The well-established safety protocols
and engineering controls used to isolate hazardous
biological materials in such laboratories address issues
that are very similar to those involved in Mars sample
return. At this time, there are several options under study
for implementing a Mars sample receiving facility.
Continuing the fundamental
“safety frst” approach to MSR, the
samples would remain securely
contained inside qualifed facilities
unless they are fully sterilized
or until they are determined by
rigorous testing to be safe for
release to other laboratories and
curation facilities. NASA and ESA
are collaborating on the sample
safety testing framework, which
will be subjected to a peer review
by outside experts before it would
be approved for use in releasing
any samples for detailed study.