Earth’s ‘evil twin’ gives up its deadly secrets

By Nic Fleming, Telegraph Science Correspondent
(Filed: 12/04/2006)

A spacecraft the size of a garden shed arrived above the planet Venus yesterday, to the obvious delight of European Space Agency scientists and engineers.

Click to enlarge
The reappearance at 9.08am of a temporarily interrupted green line on a computer screen was the signal for cheers, handshakes and the occasional hug at ESA’s spacecraft operations centre in Darmstadt, Germany.

Venus Express will spend the next 500 days collecting information on the extreme environment of Earth’s “evil twin” that will help climate researchers improve their predictions of the effects of global warming on our atmosphere.

Scientists across the world are eagerly awaiting data from the probe that will help to explain the mystery of why the Venusian environment is the most extreme and hostile in the solar system yet is so close in distance, size and origins to Earth.

The arrival of the £140 million spacecraft, whose propulsion system was built in Stevenage by the satellite specialists EADS Astrium, is only the European Space Agency’s second attempt to put a spacecraft into orbit around another planet.

Fred Taylor, Halley professor of physics at the University of Oxford and one of three scientists who designed and proposed the mission, said: “It could hardly have gone better.

“The whole mission has gone like clockwork. This shows that Europe is now a major player in this field.

“Venus was Earth’s twin but they have deviated in terms of climate. Understanding atmospheric changes from a planetary perspective can certainly help inform us about the problems we face on Earth.”

Venus Express set off on its 153-day, 26-million-mile journey after blasting off into space on a Soyuz launcher from Baikonur in Kazakhstan last November.

At 8.17am yesterday it fired its main engine for a 50-minute burn that placed it in the planet’s gravitational field. ESA technicians declared that the spacecraft had performed the manoeuvre as planned.

In theory, the planet should be a good place to look for life. It is virtually the same size, mass and density as Earth, is our closest neighbour, and was formed at about the same time, about 4.5 billion years ago, from the same materials.

In reality, it is highly unlikely that any form of life remotely similar to that on Earth could survive on the surface.

It is hot enough to melt lead, has an atmospheric pressure 92 times our own and is covered by thick clouds of sulphuric acid.

The scorching temperatures are caused mainly by a runaway greenhouse effect that keeps heat trapped in a heavy atmosphere composed of 96 per cent carbon dioxide.

As carbon dioxide emissions have increased on Earth by 30 per cent since the Industrial Revolution, climate scientists believe that the mission will provide vital clues about how increased quantities of the gas affect the atmospheric system.

Information on how Venus’s clouds affect the energy balance between the incoming and reflected solar radiation will also help to explain the mechanisms of global warming.

One key difference is that while Earth’s magnetic field prevents atmospheric gases escaping, Venus generates no magnetic field, meaning its upper atmosphere is constantly eroded by solar winds.

Scientists know from data collected by the US Magellan spacecraft – the last mission to Venus that orbited from 1990 to 1994 – that there was volcanic activity on the planet in the past. They want to know if this is still the case.

Onboard spectrometers will measure temperatures and analyse chemical composition of different levels of the atmosphere and the surface.

Cameras will produce images of both the surface and atmosphere in UV, visible and infrared wavelengths.

The ASPERA-4 instrument will study the interaction between the solar wind and the atmosphere. The first scientific results should be available next month.

Dr Andrew Coates, of University College London’s Mullard Space Science Laboratory, said: “In planetary terms Venus is our nearest neighbour, but also our worst nightmare.

It is a ‘hell on Earth’ planet. Understanding Venus’s runaway greenhouse gas effect will help us test our own atmospheric models and make more accurate predictions of changes taking place on Earth.”

Dr Colin Wilson, from Oxford University, said: “One of the big questions in the climate change debate is when the climate does change, can we still trust the atmospheric models?

“The more we can learn about how well the models work or do not work on Venus, the better we are able to answer that question.”

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