10 kilometers
Heat shield
Parachute and
backshell
InSight
InSight
Curiosity
Viking 2
Spirit
ELYS
PL IUM
ANI
TIA
WWW.ASTRONOMY.COM 21
back to haunt — but fortunately not kill
— the mission.
Is Mars alive?
Prior to InSight, planetary scientists had
a rudimentary understanding of what
the interior of Mars was probably like,
and some crude hypotheses about its
level of activity. Based on general simi-
larities among our solar system’s terres-
trial planets, and on basic physical,
compositional, geologic, and other infor-
mation about Mars provided by previous
missions, researchers also deduced that
Mars was differentiated — with an inte-
rior segregated into a core, mantle, and
crust like Earth’s.
NASA’s Mars Global Surveyor orbital
mission in the mid-1990s provided a key
piece of information supporting this
hypothesis. The spacecraft’s magnetom-
eter measured strong magnetic fields in
the rocks on certain parts of the planet’s
surface. Scientists presume these signa-
tures are remnants of what was once a
global magnetic field, perhaps similar in some ways to Earth’s. Our planet’s
magnetic field arises in the core. This
partially melted, spinning ball of highly
conductive iron creates a strong mag-
netic field that extends from the core well
out into space. The field helps shield the
surface from harmful radiation and
allowed life to emerge and thrive here.
Did Mars once have a partially molten
core that gave rise to a similarly benefi-
cial global magnetic field?
Another key piece of evidence sug-
gesting that Mars is differentiated comes
from tracking the radio signals Mars
Pathfinder and subsequent missions sent
from the surface. Landers and rovers
transmit their radio signals from a spin-
ning planet that wobbles slightly. Those
tiny wobbles stem from the fact that Mars
is not a uniform sphere, but instead has
internal variations in mass and density.
By modeling the minuscule changes in
radio signal frequency associated with
those wobbles, planetary geophysicists
can deduce the nature of the interior vari-
ations. Scientists tracking the Pathfinder
radio signals, for example, inferred that
Mars has a denser, and presumably iron-
rich, core that extends from the center of
LEFT: NASA’s InSight
spacecraft landed in
Elysium Planitia, a
relatively flat and
rock-free plain not
far north of Mars’
equator. In this
view from the Mars
Reconnaissance
Orbiter, the lander,
its heat shield, and
its parachute and
backshell spread
across about a half
mile (less than 1 km)
of martian terrain.
NASA/JPL/UNIVERSITY OF
ARIZONA
BELOW: The probe
set down about
375 miles (600 km)
north of the
Curiosity rover.
ASTRONOMY: ROEN KELLY
InSight set down within a landing ellipse that
stretched 81 miles (130 km) wide in a largely east-
west direction and 17 miles (27 km) in a north-south
direction. The red dot marks the spot where the
spacecraft landed. NASA’s 2001 Mars Odyssey
orbiter captured this background image in 2015.
NASA/JPL-CALTECH/ARIZONA STATE UNIVERSITY