Scouting the Solar System:
Robots from Earth Explore Other Planets
Mars is a curious place, for sure, but there are lots of other interesting places to explore across the broad reach of our Solar System.
Japanese probe over asteroid
click to enlarge ISAS artist concept
In fact, eight of the nine known planets in our System have been visited by interplanetary robot explorers sent out from Earth during the first five decades of the current Space Age. The Sun, comets and asteroids also have been explored by visiting spacecraft.
Now, a new era of sophisticated robot probes from Earth are on the way and planned to solve many puzzles of the Solar System. In fact, more than twenty missions are happening now or in the works for the United States, Europe, Japan, Russia and China through 2025.
Pluto
Pluto is the farthest planet from the Sun and never has been explored by human-built probes from Earth. No wonder then that NASA wants to send a probe it calls New Horizons to visit the most-distant recesses of our Solar System.
It's a long way to Pluto — something like 3.5 billion miles from Earth. The flight to Pluto would leave Earth in 2006 and arrive in the vicinity of Pluto in 2015.
Photos of Pluto and its moon Charon would be sent back along with data about the planet's atmosphere and surface composition.
It's an average 3,666 million miles from the Sun to Pluto. That compares with only 93 million miles from the Sun to Earth.
The Sun
Ulysses is a large U.S.-European spacecraft already in the vicinity of the Sun. It was launched in 1990 and arrived in 1992.
The Russians are considering a solar probe to be launched around 2006. It would fly within 4.3 million miles of the Sun.
The Moon
Japan, China, Europe and the United States all have designs on the Moon:
- NASA's Lunar Prospector already has visited the Moon. It was a 660-lb. spacecraft that orbited the Moon at an altitude of 63 miles from where it spotted evidence of ice in shaded regions of the lunar poles.
- Japan's Lunar-A orbited the Moon. The nation is planning more Moon research with a more sophisticated orbiter with lander.
- The European Space Agency (ESA) will launch its SMART-1 probe to the Moon.
- China would like to send a probe to the Moon by 2006.
Moons Read about explorations of other Moons in the Solar System
Asteroids and Comets
The only close-ups of a comet to date were snapped by the European probe Giotto which flew within 380 miles of Comet Halley in 1986. The only close-up photos of asteroids were made by NASA's Galileo spacecraft which flew by Gaspra in 1991 and Ida in 1993 on its way to Jupiter. Galileo's picture surprised everyone when it revealed a tiny half-mile-long moon orbiting the 35-mile-long Ida.
Japan, Europe and the United States have plans to send new probes to fly by asteroids or comets:
- The Near Earth Asteroid Rendezvous (NEAR) spacecraft was the first of NASA's Discovery-class spacecraft. It was launched in February 1996 on a course which will take it within 745 miles of the 38-mile-long asteroid Mathilde in the asteroid belt between Mars and Jupiter on June 27, 1997. NEAR then will fly by Earth in January 1998 on its way to the 25-mile-long asteroid Eros which orbits the Sun between Earth and Mars. In January 1999, NEAR will go into orbit around Eros, just nine miles from the asteroid. It will send back photos and data on surface elements for a year. On February 6, 2000, the spacecraft will take extremely close-up photos as it is crashed into the asteroid.
- NASA's Deep Space 1 (DS-1) spacecraft is planned for launch in July 1998 to fly by the asteroid McAuliffe in January 1999. It then will fly by Mars in April 2000 on its way to rendezvous with the comet West-Kohoutek-Ikemura in June 2000 when the comet will be 242 million miles from Earth. The first of NASA's inexpensive "New Millennium" missions, DS-1 will be the first spacecraft ever to have an ion propulsion engine as its primary source of thrust.
- Stardust, another of NASA's Discovery-class spacecraft, is planned for launch in February 1999 to fly within 62 miles of comet Wild-2 in January 2004. It will sweep up samples of comet dust and return them to Earth, the first ever return of extraterrestrial material from beyond the Moon. The dust particles will be in a 32-inch-diameter re-entry capsule which will plop down on a dry lakebed near Salt Lake City, Utah, in January 2006.
- Japan will launch its Muses-C asteroid sample return mission in January 2002 to arrive at the near-Earth asteroid Nereus in 2003. Muses-C will grab the asteroid and fire a projectile into its surface, causing debris to bounce up to be caught by the spacecraft. The sample would be returned to Earth in January 2006, the same month Stardust returns its samples.
- Rosetta, a European Space Agency (ESA) interplanetary vehicle, will be the first spacecraft to land on a comet when it completes its ten-year mission to Comet Wirtanen. Rosetta will be launched in 2003. It will fly by Mars once, Earth twice and two asteroids. Then the spacecraft will be mostly turned off and left in a hibernation mode for three years. It will be powered up again when it nears Comet Wirtanen in 2011. It will orbit 620 miles above Wirtanen for about two years to 2013. Rosetta will carry a German lander known as RoLand. It may carry a U.S.-French lander known as Champollion. RoLand will spend several months on the surface. Champollion would drill itself down eight inches below the surface.
- Clementine-1 was a U.S. Defense Dept. spacecraft which sent back a great deal of new image data from the Moon in 1994, including evidence of frozen water on the lunar surface. A new U.S. Air Force spacecraft, Clementine-2, if approved, could be sent on a year-long flight to inspect three asteroids in orbits which cross Earth's orbit. Clementine-2 would shoot projectiles into each asteroid to determine its composition.
Saturn
With the advent of smaller and cheaper probes, the last of the grand old large interplanetary spacecraft is the Saturn orbiter Cassini and its Titan moon probe Huygens. NASA will launch Cassini, with Huygens aboard, in October 1997 to arrive at Saturn in June 2004.
Cassini will work in the neighborhood of the mammoth body for at least four years, eyeing the vast spread of rings around the planet, visiting the clutch of large and small moons spinning around the big gas bag, monitoring Saturn's atmosphere and measuring its powerful magnetic field.
Meanwhile, Huygens will land on the ancient frozen world of Titan, Saturn's largest moon, to sniff the atmosphere and dig up chemical samples of the soil.
Cassini with Huygens is a joint project of NASA, the European Space Agency (ESA) and the Italian Space Agency (ASI).
Jupiter
NASA's large Galileo spacecraft already is in the vicinity of the Jupiter. It was launched in 1989, arrived in 1995 and will continue sending back data through at least 1997. In fact, NASA may extend the Galileo project to allow more flybys of the giant planet's moons.
Beyond the Solar System
Four grand old work horses from Earth are cruising at or beyond the edge of the Solar System:
- Pioneer 10 launched in 1972
- Pioneer 11 launched in 1973
- Voyager 1 launched in 1977
- Voyager 2 launched in 1977
