Planetary weather probes

Since 1962, planetary probes have been visiting planets in the solar system and sending back data about their atmospheres and weather. This information is vital for the safety and effectiveness of any missions to these places, and enables comparisons to be made with conditions on Earth.

Earth

Scientists gather huge amounts of weather data every hour from probes on Earth, in the atmosphere, and circling the planet.

Land-based weather stations across the world use a variety of instruments - and the human eye - to observe and record data, such as temperature, air pressure, cloud height and type, wind speed and direction, precipitation, humidity and visibility.

Weather radar is used to locate and track the movement of weather systems. A version called Doppler radar can detect detailed air movements deep inside clouds and thunderstorms to give early warning of tornadoes and other severe conditions.

Weather balloons (radiosondes) provide profiles of air temperature, pressure and humidity up to heights of 19 miles (30km). Tracking the balloon provides data about wind speed and direction at different heights.

Weather satellites give a continuous picture of changing weather. Visible images show cloud patterns, weather fronts, thunderstorms, dust storms and other large weather features. An array of instruments monitor patterns of temperature and upper-air winds, and the movements and life cycles of large storms. Infrared instruments are used to collect information at night.

Jupiter

In March 1972, Pioneer 10 was the first probe to send back close-up pictures of the bands of clouds which circle the planet.

The 1977 Voyager probes revealed the turbulent motion of these clouds, and gave the first glimpse of what weather on the planet must be like.

Launched in 1989, the US spacecraft Galileo provided even more detailed information about the planet's violent atmospheric activity.

Mars

Mariner 6 was the first probe to send back weather data from Mars. It flew near the planet in July 1969, sending back data on surface temperatures and atmospheric temperature and pressure.

In 1969, the Russian probe Phobos 2 was the first to detect water in the Martian atmosphere.

The 1975 US Viking orbiters sent back pictures of thin clouds swirling over parts of the Martian landscape, and the Viking landers sent back weather reports from the planet's surface until the early 1980s.

More detailed information was obtained from the US Mars Pathfinder, which landed on the planet in July 1997.

Mercury

Mariner 10 is the only space probe to have been targeted at Mercury. It made three fly-bys of the planet in 1974-5. As the planet has little or no atmosphere, there was no weather to be seen.

Neptune

Voyager 2 is the only probe to have visited Neptune, sending back photographs that reveal great storms, 1,200mph (2,000kph) winds and the first glimpse of the Great Dark Spot.

Pluto

This is the one planet in the solar system that has never been visited by a space probe.

Saturn

In November 1980, Voyager 1 sent back the first images of Saturn's weather, showing bands of clouds racing round the planet at speeds up to 1,100mph (1,800kph). It also revealed the presence of a rotating spot similar to Jupiter's Great Red Spot.

The US probe Cassini is expected to reach Saturn in June 2004.

Uranus

Voyager 2 is the only probe to have made a fly-by of Uranus. In January 1986, it sent back photos showing high clouds over part of the landscape, and a cloud of smog over the planet's south pole.

Venus

The first planetary probe to collect weather data was Mariner 2, which reached Venus in December 1962. It sent back data about the temperature and main components of the atmosphere.

In 1967, the Russian Venera 4 dropped a probe into the atmosphere of Venus. It transmitted data about the composition of the atmosphere, as well as temperature and pressure at different heights.

In 1974, Mariner 10's ultraviolet detectors revealed that the entire cloud system on Venus circled the planet once every four Earth days. More detailed information about the planet came from the US probe, Magellan, which entered orbit around Venus in August 1990.

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