New York: A strong "electric wind" may have played a significant role in stripping Venus, Earth's twin planet, of its oceans, says a new study by NASA and University College London researchers.
Venus has an "electric wind" strong enough to remove the components of water from its upper atmosphere, the study said.
"It's amazing, shocking," said Glyn Collinson, scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
"We never dreamt an electric wind could be so powerful that it can suck oxygen right out of an atmosphere into space," Collinson, who is the lead author of a paper about this research, noted.
The findings are based on ESA's (European Space Agency) Venus Express mission by NASA-funded researchers.
Venus is in many ways the most like Earth in terms of its size and gravity, and there is evidence that it once had oceans worth of water in its distant past.
However, with surface temperatures around 460 degrees Celsius, any oceans would have long since boiled away to steam and Venus is uninhabitable today.
Yet Venus' thick atmosphere, about 100 times the pressure of Earth's, has 10,000 to 100,000 times less water than Earth's atmosphere.
Something had to remove all that steam, and the current thinking is that much of the early steam dissociated to hydrogen and oxygen: the light hydrogen escaped, while the oxygen oxidised rocks over billions of years.
Also the solar wind -- a million-mile-per-hour stream of electrically conducting gas blowing from the sun -- could have slowly but surely eroded the remainder of an ocean's worth of oxygen and water from Venus' upper atmosphere.
The team discovered Venus' electric field using the electron spectrometer, a component of the ASPERA-4 instrument, aboard the ESA Venus Express.
The team found that the field was at least five times more powerful than at Earth.
The findings were published in the journal Geophysical Research Letters.
"We don't really know why it is so much stronger at Venus than Earth, but, we think it might have something to do with Venus being closer to the sun, and the ultraviolet sunlight being twice as bright,” Collinson said.
The researchers believe that another planet where the electric wind may play an important role is Mars.
NASA's MAVEN mission is currently orbiting Mars to determine what caused the Red Planet to lose much of its atmosphere and water.
Taking the electric wind into account will also help astronomers improve estimates of the size and location of habitable zones around other stars.
"This is something that definitely has to be on the checklist when we go looking for habitable planets around other stars," Collinson noted.