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British Mission to Venus Would Unravel Planets Weather Secrets

Posted on: Saturday, 24 April 2004, 06:00 CDT

British scientists are working on the ultimate long-range weather report - a study of the hurricane winds and bizarre clouds of Venus.

They plan to drop a procession of tiny "smart probes" the size of golf balls from a weather balloon drifting high over the Earth's mysterious near neighbour, to measure light levels, temperatures and wind speeds at various altitudes beneath the clouds of sulphuric acid that mask the planet's surface.

The mission is so far little more than a twinkle in the eye of the European Space Agency.

But engineers and scientists at Qinetiq, the former British government defence research agency, are already studying designs for probes that will be light enough to fall slowly, sturdy enough to survive winds of more than 200mph, insulated enough to function through a change of up to 500C (900F) as they tumble from the frozen Venusian stratosphere to its baking bedrock, and tough enough to carry on working through an acid bath.

They also have to think of a way of following the probes' progress. So the researchers must also devise a lightweight, miniature meteorological of fice suspended below the balloon to track the probes, collect the data and relay it back to Earth via an orbiting satellite.

"It will detect an object the size of an apple 100 miles away through clouds of acid. This is no small task," said Nigel Wells, who leads the Venus project at Qinetiq.

"At the very top, where the balloon will be flying, it will be really quite cold, perhaps 100C below zero. So these little probes are going to go through quite a large temperature range. They will start off very very cold and end up basically at 400C."

The probes are unlikely to survive once they hit the Venusian surface, where the rocks are at roughly the melting point of lead (327C/621F).

Venus is a textbook example of the runaway greenhouse effect: its dense, moist atmosphere has trapped solar radiation and turned what might have been a suitable home for life into a murderous acid bath.

The Europeans plan a mission to the solar system's brightest planet in 2005. Venus Express will carry much the same instrumentation as the Mars Express mission now flying over the red planet, gathering radar and other data from the top of its atmosphere to several hundred metres below its bedrock surface.

But because the Venusian atmosphere is so opaque, the researchers have to think of another strategy to study its mysterious weather patterns. The Venus weather mission could start within a decade.

Qinetiq researchers are working with Oxford University and an Italian partner on ways to design up to 100 probes, to be released a few at a time over a period of several weeks as the balloon drifts between the poles and equator of Venus.

But they must also make sure of monitoring the progress of the pocket-sized explorers. The challenges are huge.

"Because they are so tiny, they won't have a great deal of thermal inertia. They are going to heat up very quickly. They are going to cook," said Mr Wells.

"Wind speeds are high - 100 metres a second - so there is going to be quite a lot of cross track or drift. They won't just drop in a straight line, they will drift sideways. We have aerodynamicists at Farnborough who are worrying about this at the moment.

"You want a probe to drop relatively slowly: the scientists would like a data point every 100 metres down. That means you'd like a high-drag device.

"If you make it drop very slowly, then the winds will take it so far sideways that your radar tracking system in the balloon is going to have difficulty seeing right out to the extreme angle, horizontally, where it has drifted off to. So there has to be a compromise."

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