WWW.ASTRONOMY.COM 19
As the
most
explored
world in the solar system
(save Earth), Mars has enjoyed
the lion’s share of planetary
research funding for several
decades. We’ve come a long
way since Italian astronomer
Giovanni Schiaparelli first
mapped his martian canali
(“channels,” which was mis-
translated to “canals”) in- Nearly a century later,
in 1965, NASA accomplished
the first up-close and personal
f lyby of Mars with Mariner 4.
In the decades since, dozens
more spacecraft have incre-
mentally advanced our under-
standing of the Red Planet.
Orbiters have thoroughly
mapped Mars’ surface.
Landers have probed the
planet’s internal structure and
monitored the local weather.
Rovers have trundled across
the desertscape to collect and
analyze rock samples. And
one small NASA helicopter
named Ingenuity recently
zipped through the martian
atmosphere more than a
dozen times — no small feat
considering Mars’ air is just
1 percent as dense as Earth’s.
This opens the door to future
fleets of flying scouts that
could explore broad swaths
of the planet at an incredible
pace.
Thanks to humanity’s
legion of robotic martian sur-
veyors, we now know the
rusty world was not always as
arid and inhospitable as it is
today. Because Mars is cov-
ered in networks of valleys
and deltas that once carried
rivers and fed long-lost lakes,
scientists are confident liquid
water once f lowed freely
across its surface. Rock and
soil samples plucked right off
the ground and analyzed on
the spot back up that history,
as many could have only
formed in the presence of
copious liquid water.
Although rovers tend to get
most of the credit, orbiters
have contributed just as much
to our understanding of Mars’
past. For instance, a 2018
study published in Geology
based on high-resolution pho-
tos taken by NASA’s Mars
Reconnaissance Orbiter ana-
lyzed dozens of martian outlet
canyons carved out by flowing
water that snaked from
ancient lakes. The researchers
found that the topography of
the many outlet canyons
matches what they’d expect if
they had all rapidly formed
during a massive and cata-
strophic f looding event some
3.5 billion years ago.
Such evidence for vast
amounts of liquid water hav-
ing once flowed on Mars islargely why NASA’s latest
rover, Perseverance, is cur-
rently searching for signs of
ancient martian life. But
the possibility of past
life isn’t the world’s
only appeal.
Compared to
Mercury, Venus,
and the giant
planets, Mars
could offer a
somewhat
suitable
place for
humanity to
eventually
set up shop
— if, of
course, we
can harvest
and make what
we need there.MARS
STATS
Mass: 0.11 Earth masses
Diameter: 4,220 miles
(6,790 km)
Surface temperature:
68 F (20 C) to –243 F (–153 C)
Rotation period (day):
24 hours 37 minutes
Orbital period (year):
687 Earth days
Moons: Phobos and DeimosLEFT: NASA’s Curiosity rover
poses for a selfie in front of
a 20-foot-tall (6 m) rock
formation named Mont
Mercou. This panorama was
stitched together from a total
of 71 images taken by two
cameras mounted on the
rover’s arm and head.
NASA/JPL-CALTECH/MSSSBELOW: The Hubble Space
Telescope’s Wide Field and
Planetary Camera 2 snapped
the four images used to create
this nearly global, full-color
map of Mars. STEVE LEE (UNIVERSITY OF
COLORADO)/JIM BELL (CORNELL UNIVERSITY)/
MIKE WOLFF (SPACE SCIENCE INSTITUTE)The Viking Orbiter provided
the images used to create
this global color map of Mars’
scarred and ice-capped surface,
which is seen at a resolution of
about 0.6 mile (1 km) per pixel.
NASA/JPL-CALTECH/USGS