It’s the U.S. space agency’s most ambitious and expensive Mars mission
yet and it begins with the Red planet arrival on Sunday of the smartest
interplanetary rover ever built.
It won’t be easy. The complicated touchdown NASA designed for the
Curiosity rover is so risky that it’s been described as “seven minutes
of terror” — the time it takes to go from 20,920 kmph to a complete
stop.
Scientists and engineers will be waiting anxiously as the spacecraft
plunges through Mars’ thin atmosphere and, in a new twist, attempts to
slowly lower the rover to the bottom of a crater with cables.
Scientists on Earth won’t know for 14 minutes whether Curiosity lands
safely as radio signals from Mars travel to Earth. If it succeeds, a
video camera aboard the rover will have captured the most dramatic
minutes for the first filming of a landing on another planet.
“It would be a major technological step forward if it works. It’s a big
gamble,” said American University space policy analyst Howard McCurdy.
The future direction of Mars exploration is hanging on the outcome of
this $2.5-billion science project to determine whether the environment
was once suitable for microbes to live. Previous missions have found ice
and signs that water once flowed. Curiosity will drill into rocks and
soil in search of carbon and other elements.
Mars is an unforgiving planet with a hostile history of swallowing
man-made spacecraft. It’s tough to fly there and even tougher to touch
down. More than half of humanity’s attempts to land on Mars have ended
in disaster. Only the U.S. has tasted success.
“You’ve done everything that you can think of to ensure mission success,
but Mars can still throw you a curve,” said former NASA Mars-specialist
Scott Hubbard, who now teaches at Stanford University.
The Mini Cooper-sized spacecraft travelled eight and a half months to
reach Mars. In a sort of celestial acrobatics, Curiosity will twist,
turn and perform other manoeuvres throughout the seven-minute thrill
ride to the surface.
Why is NASA attempting such a daredevil move? It had little choice.
Earlier spacecraft dropped to the Martian surface like a rock, swaddled
in airbags, and bounced to a stop. Such was the case with the much
smaller and lighter rovers Spirit and Opportunity in 2004.
At nearly a ton, Curiosity is too heavy, so engineers had to come up
with a new way to land. Friction from the thin atmosphere isn’t enough
to slow down the spacecraft without some help.
During its fiery plunge, Curiosity brakes by executing a series of
S-curves similar to how the space shuttle re-entered Earth’s atmosphere.
At 1,450 kph, it unfurls its huge parachute. It then sheds the heat
shield that took the brunt of the atmospheric friction and switches on
its ground-sensing radar.
Curiosity then jettisons the parachute and fires up its rocket-powered
backpack to slow it down until it hovers. Cables unspool from the
backpack and slowly lower the rover at less than 3.2 kmph. The cables
keep the rocket engines from getting too close and kicking up dust.
Once the rover senses touchdown, the cords are cut.
Even if the intricate choreography goes according to script, a freak
dust storm, sudden gust of wind or other problems can mar the landing.
The rover’s landing target is Gale Crater near the Martian equator.
Scientists know Gale was once waterlogged. Images from space reveal
mineral signatures of clays and sulphate salts — which form in the
presence of water — in older layers near the bottom of the mountain.
During its two-year exploration, the plutonium-powered Curiosity will
climb the lower mountain flanks to probe the deposits. As sophisticated
as the rover is, it cannot search for life. Instead, it carries a
toolbox including a power drill, rock-zapping laser and mobile chemistry
lab to sniff for organic compounds, considered the chemical building
blocks of life. It also has cameras to take panoramic photos. Curiosity
will explore whether the crater ever had the right environment for
microorganisms to take hold.
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