Although a world stripped of water and melted by temperatures hot enough to liquefy lead, Venus may once have been a planet much like Earth. The vast oceans could have supported life, according to the latest discoveries of Venus Express, a European Space Agency (ESA) craft launched in November 2005 to investigate our "sister" planet.

"Our new data make it possible to construct a scenario in which Venus started out like the Earth, possibly including a habitable environment, billions of years ago, and evolved to the state we see now," said Professor Fred Taylor of Oxford University.

Once considered Earth’s twin planet, Venus became inhospitable for life due to a series of change events. The planet’s history led to loss of water, an atmosphere clogged with carbon dioxide and a runaway effect that gave rise to severe global warning.

The Venus Express, which has been orbiting Venus since 2006, has also helped to conclude why the climate of this planet is so severe, according to Prof. Taylor.

 "It is now becoming clear why the climate on Venus is so different from Earth, when the planets themselves are otherwise quite similar," he said.

Venus Express is loaded with scientific instruments, which makes possible to monitor a suite of phenomena, such as the amount of heavy water vapor in the atmosphere and the strength of any magnetic field.

Venus is the closest planet to Earth in terms of its distance from the Sun, its mass, radius, density and chemical composition. Venus differs in terms of slow rotation – once every 243 Earth days, which contributes to differences in its climate.

"These differences are not just down to Venus being closer to the Sun. We now know that the lack of a protective magnetic field and the differing planetary rotation rates also play a role in ensuring many of the atmospheric processes we observe on Earth occur at a much faster rate on Venus,” Prof. Taylor said.

Venus Express has confirmed that the lack of a magnetic field made Venus vulnerable to water-stripping properties of the solar wind. The carbon dioxide has been released into Venus atmosphere causing a runaway greenhouse effect, with surface temperatures averaging about 450C by day compared to the oceans on Earth, which have been critical in trapping carbon dioxide as carbonate rocks.

"The findings show, of course, that the planet as it stands now is different from the Earth -- the high temperatures, the high pressures and the composition. But the processes, we now understand, are much more Earth-like. The two planets were, in fact, very similar in the earlier days of the solar system. And they have then evolved in different directions, but according to the same rules and explanations," Hakan Svedhem, Venus Express team project scientist, said in a telephone interview, according to Reuters.

Due to hot temperatures registered on Venus, almost 457C by day and up to 240C by night, “the oceans boiled off and all the water ended up as water vapor in the atmosphere,” said Svedhem.

Instrument on Venus Express allowed the scientist to notice that the main ions escaping Venus’s atmosphere are oxygen, helium and hydrogen. Moreover, hydrogen and oxygen ions were shown to be escaping in the same proportions as they are found in water, H2O, providing a likely mechanism for how water has been leaving Venus.

A previous mission to Venus had detected shadows of lighting through the planet’s atmosphere. The instruments aboard Venus Express detected the same thing.

"They look like lightning bursts, very short discharges of electrical energy," said Christopher Russell of the Institute of Geophysics and Planetary Physics at the University of California, Los Angeles. This is a significant finding, as on Earth lightning creates chemical reactions and molecules that some believe could be precursors to life.

"Now Venus is an unpleasant sulphuric place and we don't expect it has the atmosphere for life but who knows at the beginning?" author Christopher Russell of the University of California, Los Angeles told the CBC News. Now the atmosphere on Venus is similar to "19th century London on a smoggy day with sulphuric acid in the air and a general haze."

Temperatures on Venus register high differences between day and night. Venus Express found differences of 30 to 40 degrees, which is “puzzlers” according to Russell.

"And puzzles are always interesting because they shake up your prejudices and open your eyes to things," he said.

Violent winds were also detected in the planet’s upper atmosphere. At 43 miles (70 kilometers) above Venus’s surface wind speeds reached 225 miles (360 kilometers) an hour.

The latest findings are reported in this week’s issue of the journal Nature.