Solid
inner
coreCoreLiquid
outer coreMantle
CrustEarth
Mars
The Moon
Mantle
Core CrustCrust6 to 31 miles
(10 to 50 km)1,404 miles
(2,260 km)1,780 miles
(2,865 km)16 miles
(25 km)3,959 miles (6,371 kilometers)771 to 1,168 miles
(1,240 to 1,880 km)758 miles
(1,220 km)932 to 1,305 miles
(1,500 to 2,100 km)2,106 miles (3,390 km)714
miles
(1,147 km)298
miles
(480 km)1,080 miles (1,737 km)68 miles
(110 km)SolidLiquidMoltenMantle
22 ASTRONOMY • OCTOBER 2019
the world out to somewhere between
40 and 60 percent of the planet’s radius.
But is that core still at least partially
molten? Does Mars have enormous
quantities of internal heat — high heat
f low, in geophysical terms — like Earth,
and does that heat drive contemporary
geologic processes? Mars has no global
magnetic field today, which is one argu-
ment that the core has solidified and the
interior is no longer active.
Other arguments against high heat
f low include the absence of any proof for
recently active volcanoes or hotspots, as
well as no convincing evidence for past
or present plate tectonics. Earth’s crust is
divided into a dozen or so large tectonic
plates. These plates move relative to one
another, causing most of our planet’s
earthquakes and volcanoes, and play a
role in helping our planet release its inter-
nal heat. But from orbit, Mars appears to
be a one-plate planet with no obvious
internal geologic activity. Could surface
observations verify this supposition?The view from Elysium
The InSight mission team worked franti-
cally for four years to design, build, and
test the lander and its instruments in
time to meet the planned 2016 launch.
The task proved challenging because a
number of technical and management
problems cropped up along the way. The
most serious of these was a small leak in
the housing for the seismometer, which
needs to operate in a vacuum to achieve
its required sensitivity, discovered several
months before the scheduled launch.
The instrument, built by a European
consortium led by the French Space
Agency (CNES), could not be repaired
in time and the launch was delayed for
two years. NASA estimated the cost
of this delay at around $150 million,
canceling out the hoped-for savings
from relying on a heavily international
science payload.
The delay also had ramifications
within NASA. The space agency realized
that highly technical internationalcollaborations can be exceedingly diffi-
cult to manage and decided to tighten
the rules on how much outside countries
could contribute to instruments on future
missions. The new limit is now one-third
the total cost of all instruments.
The delay did give JPL, Lockheed,
and their international partners time
to diagnose and repair the problems,
and to test the full system in a giant,
Mars-simulating vacuum chamber
at Lockheed’s facility in Colorado.
Technicians then packaged the spacecraft
into its protective cruise-stage aeroshell
and heat shield and shipped it to
Vandenberg Air Force Base in California,
where it would become the first inter-
planetary mission launched from the U.S.
West Coast. NASA chose Vandenberg
over the usual Cape Canaveral Air Force
Base launch facility in Florida because it
could better handle the spacecraft’s large
mass and gave more f lexibility in timing
the launch. In the wee hours of May 5,
2018, an Atlas V rocket lit up the skiesGeologists have mapped out the interiors of Earth and the
Moon quite well, thanks to an array of seismometers on our
planet and a handful left on our satellite by Apollo
astronauts in the late 1960s and 1970s. Although
Mars’ interior remains more enigmatic,
scientists hope InSight will change that.
ASTRONOMY: ROEN KELLY, AFTER NASA/JPLPeering beneath the surface