The Washington Post - USA (2020-07-28)

TUESDAY, JULY 28 , 2020. THE WASHINGTON POST EZ RE A

BY JOEL ACHENBACH

A $2.7 billion NASA rover is
scheduled to blast off for Mars on
Thursday on a mission that could
help solve one of the greatest myster-
ies in all of science: the origin of life.
If all goes as planned, the rover,
named Perseverance, will collect
rock and soil samples that would
later be space-mailed back to
Earth for close scrutiny. Scientists
will be looking for fossils or “bio-
signatures” of o rganisms that may
have thrived about 3 billion years
ago when the Red Planet was
much warmer and wetter.
“We have one data point for life
on a planet,” said planetary geolo-
gist Bethany Ehlmann of the Cali-
fornia Institute of Technology,
part of the science team for Perse-
verance. “Mars is the second data
point. We know from the invest-
ments that we’ve made from ex-
ploration that there was this hab-
itable world right next door. Right
about the time that Earth was
developing its life, Mars was also
habitable, with lakes and rivers.”
A close match between ancient
Martian life and life here on Earth
would suggest a common origin,
with one planet seeding the other
through meteorites. Or perhaps
Mars had life-forms of a c omplete-
ly alien nature. Or maybe they
never existed a nd Mars has a lways
been a sterile world.
“Is it a foregone c onclusion that
as long as you have the right mix,
things are going to happen and
you’re going to end up with life?”
said Mary Voytek, head of NASA’s
astrobiology program. “We don’t
really have the answer to that.”
The new rover mission is offi-
cially known as Mars 2020, and it
is the first part of a multiphase
project called the Mars Sample
Return c ampaign, o nly this l eg h as
been fully funded by Congress.
Perseverance will launch from
Florida’s Cape Canaveral atop an
Atlas V rocket. It will be the second
robotic mission to Mars in the span
of a week: China on Thursday
launched its own probe, named
Tianwen-1, which is that country’s
first attempt to land a c raft o n Mars.
While coping with additional
challenges introduced by the coro-
navirus pandemic, NASA h as been
racing a gainst a deadline imposed
by physics: There’s a narrow win-
dow when the Earth and Mars are
properly positioned in their or-
bits. Perseverance must launch by

Aug. 15, after which the effort

would have to be put on hold for a

couple of years. It is slated to land

on Mars on Feb. 18.

The engineering demands of

any robotic mission are enor-

mous. Perseverance will have to

descend to the surface of Mars in

the notoriously confounding at-

mosphere — it’s t oo thin to be very

helpful with braking but just thick

enough to cause aerodynamic

trouble — and land in one piece,

upright and f unctional. T hat is not

an uncontested layup.

The mission will benefit from

autonomous navigation sensors

that should allow a pinpoint land-

ing in Jezero Crater, where a river

delta once flowed into a deep lake

— a site p ainstakingly selected by

scientists as the kind of place that

might host remnants of ancient

organisms.

Perseverance i s being described

by NASA as part of its long-term

plan for a human mission t o Mars.

The rover carries an instrument

that can manufacture oxygen out

of Mars’ carbon dioxide-rich at-

mosphere, a process critical to fu-

ture human missions. The rover

also carries a small helicopter,

named Ingenuity, which will per-

form the first rotorcraft flight on

another planet.

A geologist’s dream world

Life as w e know it here on Earth

is both a stonishing in its complex-

ity and strangely ordinary. The

simplest organism has a fairly

elaborate genetic code. At the

same time, it is built with some of

the most common elements in the

universe, such as hydrogen, nitro-

gen, carbon and oxygen.

In the past quarter-century,

meanwhile, astronomers have

learned t hat most stars have orbit-

ing planets, theoretically offering

plenty of potential real estate

where life might be found. But

although scientists are generally

optimistic that there is l ife beyond

Earth, they lack proof.

Their search is complicated by

the lack of a watertight definition

of life. It’s clearly something that

chemistry can achieve given the

right conditions. A living thing is

self-sustaining and structurally

coherent. It obtains energy from

the world and does something

with it. It contains the code of

information that allows it to repli-

cate, and does so with enough

inexactitude to allow natural se-

lection to work its wonders.

The quest to understand its ori-

gin on Earth is also made more

challenging by the fact that this

isn’t the planet it used to be. The

Earth’s surface has been buried,

melted, metamorphosed, eroded,

crushed, frozen and flooded.

There aren’t that many old rocks

around.

Mars, by contrast, is a geolo-

gist’s dream world. Unlike Earth,

Mars lacks plate tectonics. As a

result, the Martian surface hasn’t

been radically altered over the

past 4 billion years the w ay E arth’s

has.

“Those rocks still exist where

they were deposited with no com-

plicated overprinting,” Ehlmann

said.

Even if the mission doesn’t find

signs of life, it might detect “some

kind of prebiotic phase of life,”

said Benjamin Weiss, a Massachu-

setts Institute of Technology pro-

fessor who is part of the Persever-

ance science team.

“If we could bring back a fossil

record, a rock r ecord, some kind of

geological samples, that have

some record of that prebiotic

phase of the evolution of life, that

would arguably be as exciting, or

arguably more exciting, than find-

ing life,” Weiss said.

Past controversies

Mars has a knack for fooling

human beings, e specially those ea-

ger to discover Martian life. In the

late 19th century, astronomer Per-

cival Lowell famously claimed to

see canals on Mars, which he pos-

ited as the handiwork of a civiliza-

tion struggling with the d rying out

of the planet. That notion helped

inspire H.G. Wells’s “The War of

the Worlds,” the canonical alien-

invasion tale.

The canals were, of course,

imaginary, but well into the 20th

century, some scientists thought

Mars might be showing signs of

seasonal vegetation. Then came

the S pace Age, and t he first robotic

probe to fly by Mars, Mariner 4 in

196 5, captured images of a cra-

tered and parched landscape.

NASA’s extraordinary Viking

mission put two robotic landers

on the planet in 1976 and per-

formed several life-detection ex-

periments. O ne result l ooked posi-

tive and briefly generated eupho-

ria a mong t he scientists, b ut w hen

all t he d ata came in, the consensus

was that the experiments hadn’t

found signs of life.

The field of astrobiology re-

ceived a boost i n 1996, when scien-

tists announced they had found

what looked like fossilized micro-

organisms in a Mars rock discov-

ered in Antarctica after striking

the E arth as a meteorite. T he r ock,

scientists said, had been blasted

off Mars and into space by an

asteroid impact.

The Mars rock generated tre-

mendous media attention, but the

microfossils discovery did not age

well. Although never fully re-

solved — there are partisans on

both sides of the issue — the con-

sensus is that intriguing features

in the Mars rock (officially

ALH 8400 1) could be produced

non-biologically.

“We learned a r eally hard l esson

in 1996,” said NASA’s Voytek.

Thomas Zurbuchen, the head o f

science at NASA, said the findings

from Martian meteorites that land

on Earth are inherently enigmatic,

because they have been heated

when ejected from Mars and lack

the kind of geological context that

scientists need.

“Clearly those rocks do not an-

swer the questions that we have.

They don’t have the context and

they don’t have the careful han-

dling that it takes to make the

sample valuable,” Z urbuchen said.

Perseverance is an SUV-size

rover that looks like a fraternal

twin of Curiosity, the NASA rover

that is still exploring the planet.

Among other achievements, Curi-

osity discovered organic mole-

cules in 3-billion-year-old mud-

stones, although such carbon-

based m olecules c ould have a n on-

biological origin. Perseverance

has different tools, including new

high-resolution cameras and oth-

er remote-sensing instruments.

A discovery of life beyond

Earth, even in fossil form, would

be so significant that scientists

want t o make sure t hey get it right.

That’s one reason they want to see

Mars samples up close, back on

Earth, in facilities where the m ate-

rial can be studied for decades to

come.

Finding the best samples

Perseverance is equipped w ith a

drill and 31 canisters. After scout-

ing out the most inviting sites,

aided by aerial surveillance from

the helicopter, the rover will drill

into the surface, put Martian soil

and rock cores into the canisters,

and then leave them scattered

around the planet’s surface the

way Hansel and Gretel dropped

bread crumbs s o they wouldn’t g et

lost in the woods.

A subsequent rover would then

collect t hem in 2 026 and put them

into a launch vehicle to be blasted

into orbit around Mars. They

would then be transferred to an

orbiting spacecraft, which would

carry t he m aterial b ack to Earth i n

203 1, under current NASA plans.

Given the project’s complexity,

it is critical that the rover pick the

right samples, said Abigail All-

wood, a geologist at NASA’s Jet

Propulsion Laboratory and the

lead scientist for one of the rover’s

remote-sensing instruments.

The exact itinerary — where the

rover will drill and when — remains

undetermined. Allwood said she

hopes there is abundant time to

study the environment first.

“A s a geologist, I know the im-

portance of time in the field, look-

ing at the rocks. The more time

you s pend looking at t he r ocks, t he

better you’re going to understand

any potential biosignatures,” All-

wood said.

She makes a field geologist’s

point about what such life would

look like: multiplicative. Life cop-

ies itself.

“If it’s life, it would not be just

one. It w ill b e multiple examples of

whatever you are looking at,” she

said.

[email protected]

Rover, launching Thursday, to prowl a ncient Mars lake bed for signs of life

NASA/JET PROPULSION LABORATORY-CAL TECH/ASSOCIATED PRESS

Engineers and technicians insert sample tubes into the belly of the Perseverance Mars rover in May at

the Kennedy Space Center in Florida. The rover is scheduled to land on Mars in February.

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