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.