greenhouse effect has heated the planet’s surface to a smoldering 470˚ Celsius,
perhaps evaporating ancient oceans.
Venus also appears to have lightning and
ozone, new Venus Express observations
suggest. And the planet shows signs of
recent geological activity, with hot spots
resembling those beneath Hawaii.
on sister planet
By Nadia Drake
Venus Express has mapped heat
patterns on the planet’s Idunn Mons
peak, depicted here. Red is warmest.
Like many siblings, Venus and Earth bear a familial resem- blance. Venusissimilarto Earth in size, composition and gravitational pull. But some peculiar quirks,
from sulfuric acid clouds to swirling
polar vortices, make Venus a twisted
New results from the European Space
Agency’s Venus Express spacecraft,
which has been orbiting the cloud-shrouded planet since 2006, suggest that
beneath the acidic cloak lies an extreme
world that provides an important
point of comparison for understanding
“The more we actually get results from
Venus, the more we see how important
it is to study Venus if we want to learn
more about the Earth and planetary
systems in general,” says Venus Express
project scientist Håkan Svedhem, who
works for the European Space Agency
out of Noordwijk, the Netherlands.
Venus, like Earth, has an atmosphere.
But while Earth’s mainly comprises
nitrogen and oxygen, Venusian air is
mostly carbon dioxide. A runaway
Scientists know that planets with warm
interiors need some way to cool off.
Earth is covered with a patchwork of
tectonic plates that release heat as they
jostle and slide, yet Venus appears to be
insulated by one large, solid lid.
“That’s always been a puzzle,” says
Suzanne Smrekar of the Jet Propulsion
Laboratory in Pasadena, Calif. “How is
that heat coming out?”
It has long been suspected that vol-
canic processes might be releasing heat
accumulating in the planet’s interior,
because water vapor and sulfur dioxide
in the atmosphere are probably prod-
ucts of volcanic outgassing. Crater dating
has revealed resurfacing, possibly from
volcanoes, within the last billion years.
But until Smrekar used a spectrometer
aboard Venus Express to look at the
planet’s sweltering surface, there was
little evidence for recent volcanism.
Some regions in the southern hemi-
sphere, she found, are emitting more
heat than others. The warm areas,
which appear to be younger, resembled
volcanic terrains on Earth, complete
with basaltic lava flows. Venus hosts at
least nine volcanic hot spots, or mantle
plumes, similar to the plumes thought
to power the Hawaiian island chain,
Smrekar and colleagues suggested in
Science last year. She estimates that the
present flows are between 250,000 and
2. 5 million years old.