325
speed to reach the Gale Crater, an
ancient crater caused by a massive
meteorite impact. A parachute
slowed the craft to about 200 mph
(320 km/h), but this was still too
fast for a landing. It continued to
slow its descent over a flat region
of the crater, avoiding the 20,000-ft
(6,000-m) mountain at its center.
The craft reached about 60 ft
(20 m) above the surface and then
had to hover, since going too low
would create a dust cloud that
might wreck its instruments. The
rover was finally delivered to the
surface via a rocket-powered
hovering platform called a sky
crane. The sky crane then had to
be detached and blasted clear of the
area so that its eventual impact did
not upset any future exploration.
Having survived the landing,
Curiosity signaled to Earth that
it had arrived safely. Curiosity’s
power supply is expected to last
at least 14 years, and the initial
two-year mission has now been
extended indefinitely. So far, it has
measured radiation levels, revealing
that it may be possible for humans
to survive on Mars; discovered an
ancient stream bed, suggesting a
past presence of water and perhaps
even life; and found many of the key
elements for life, including nitrogen,
oxygen, hydrogen, and carbon. ■THE TRIUMPH OF TECHNOLOGY
ExoMars
In 2020, the European Space
Agency, in collaboration with
the Russian space agency,
Roscosmos, will launch its
first Mars rover, ExoMars
(Exobiology on Mars), with
the goal of landing on Mars
the following year. In addition
to looking for signs of alien life,
the solar-powered rover will
carry a ground-penetrating
radar that will look deep
into Martian rocks to find
groundwater. The ExoMars
rover will communicate with
Earth via the ExoMars Trace
Gas Orbiter, which was
launched in 2016. This system
will limit data transfer to
twice a day. The rover is
designed to drive by itself;
its control software will build
a virtual model of the terrain
and navigate through that.
The rover software was taught
how to drive in Stevenage,
England, at a mockup of the
Martian surface called the
Mars Yard (above).
The ExoMars rover is
expected to operate for at
least seven months and to
travel 2.5 miles (4 km) across
the Martian surface. It will be
delivered to the surface by a
robotic platform that will then
remain in place to study the
area around the landing site.
0 6 12 18 24Distances traveled by extraterrestrial rovers
Opportunity
2004–present
Mars: 26.6 miles
(42.8 km)DISTANCE IN MILESSpirit
2004–2010
Mars: 4.8 miles
(7.7 km)Curiosity
2011–present
Mars: 8.1 miles
(13.1 km)Sojourner
Jul.–Sep. 1997
Mars: 0.06 miles
(0.1 km)Lunokhod 2
Jan.–Jun. 1973
moon: 24.2 miles
(39 km)Apollo 17 Rover
Dec. 1972
moon: 22.2 miles
(35.74 km)Lunokhod 1
1970–71
moon: 6.5 miles
(10.5 km)