Scientists launch interplanetary missions to study the
planets, asteroids, and comets close up. Mariner 2 was the first successful
interplanetary craft flying past Venus in 1962. MARS EXPLORATION
began with Mariner 4 in 1965. Since then all the planets except Pluto have been
visited by interplanetary craft. Some spacecraft study their targets as they
fly by, some orbit their targets, and others even land on them.
The Magellan spacecraft went into orbit around Venus in 1990. It
used radar to find out what lay beneath the clouds that permanently cover the
planet. The images it sent back showed that the landscape of Venus was covered
in huge lava flows from hundreds of volcanoes. There were also spidery cracks,
called arachnoids, in the planet’s surface.
A spacecraft called NEAR-Shoemaker made an unexpected landing on the
asteroid Eros in February 2001. It had spent the previous year in orbit around
the 33-km (21-mile) rocky body, which sometimes comes within 22 million km (14
million miles) of Earth. At the end of the mission, the scientists decided to
let the craft get closer and closer to the surface, taking pictures as it went.
To their surprise, the craft survived quite a hard landing on the asteroid, and
one instrument continued to work for several days afterwards.
DESTINATION SATURN AND TITAN
In 2004 the Cassini spacecraft reached the beautiful ringed planet
Saturn after a seven-year journey from Earth. The aim was to study the planet
and many of its moons over a long period of time. Cassini was programmed to
release a probe called Huygens into the thick atmosphere of Saturn’s
largest moon, Titan, and to land it on the moon’s surface.
Some of the most exciting interplanetary missions have
been to Mars, our neighbouring planet. Mars is the only other planet where life
may once have existed and where human beings could possibly settle in the
future. Mars is being explored in depth by spacecraft on its surface and in
orbit around it. These missions have found a lot of frozen water in the Martian
rocks, perhaps all that is left of ancient Martian oceans.
In January 2004, two robot vehicles called Spirit and Opportunity
touched down on Mars and began moving slowly over the surface. They carried
instruments to study rocks, and cameras to take pictures of the surface, and
for navigation. Before every stage of exploration, each rover took pictures of
the area directly ahead. These were used to plan a route, avoiding hazards, to
the next target area.
The Mars Global Surveyor was launched in 1996 and reached Mars
orbit 10 months later. In 1999, it began its main mission: to orbit the planet
acquiring data in order to create a detailed picture of the Martian surface. It
also mapped the topography (the three-dimensional landscape) of the planet, and
studied the surface rocks and the atmosphere.
