Despite
being
the mostbrilliant planet in our sky,
Ve nu s o f f e r s l i t t l e v i s u a l
oomph when observed from
afar. (See “Unveiling Venus”
on page 48.) That’s because its
surface is shrouded by thick,
omnipresent clouds. These poi-
sonous puffs trap heat that would
otherwise escape into space, making
it the most sweltering planet in the solar
system — hot enough to melt lead on its
surface. But don’t worry about burning
up: If you were to stand there, the atmo-
sphere (made mostly of carbon dioxide
laced with sulfuric acid) is so dense that
the pressure would collapse your lungs
and kill you instantly.
Despite its hellish environment, Venus
holds many fascinating mysteries. For
one, it’s strikingly similar to Earth in size
and composition. And yet, the worlds
have clearly led two very different lives,
with Venus experiencing a runaway
greenhouse effect in its past. Unlike
Mercury, whose bulky iron core accounts
for some 75 percent of the planet’s mass,
the core of Venus is thought to be rela-
tively earthlike: differentiated into a solid
inner core and a molten outer core.
However, Venus does not internally gen-
erate a discernible magnetic field like
Earth does, which might be because it
rotates (backward) so slowly that a venu-
sian day is longer than a venusian year.
Steadily, though, Venus is revealing
some of its secrets. The veil created by its
clouds was finally lifted in 1994, when the
Magellan spacecraft completed
a five-year mission that, among other
things, used cloud-penetrating radar to
map some 98 percent of the world’s
cloaked surface. As incredible as
Magellan’s work was, however, a trio
of new spacecraft recently selected to
explore Venus in the next decade are
sure to raise the bar even higher.
On June 2, NASA announced not one,
but two complementary missions to
Venus: DAVINCI (short for DeepAtmosphere Venus Investigation
of Noble gases, Chemistry, and
Imaging) and VERITAS (Venus
Emissivity, Radio Science, InSAR,
Topography & Spectroscopy). The for-
mer will dive through Venus’ atmosphere,
snapping pics of the environment and
sampling the world’s acidic clouds before
slamming into its surface. That bold plan
will allow scientists to stitch together a
layer-by-layer profile of Venus’ atmo-
sphere — and perhaps even confirm the
f loating phosphine detected there last
year, which tantalized many because it
is often produced by microbial life on
Earth. Meanwhile, VERITAS will orbit
Venus, using radar and imaging equip-
ment to investigate whether the world is
actively experiencing volcanic activity
and, if so, learn what might be driving it.
And don’t forget EnVision, the
European Space Agency’s contribution.
This orbiting craft will use a sounder to
study Venus’ underground layering, radar
to map its surface, spectrometers to ana-
lyze trace atmospheric gases, and a radio
experiment to probe the planet’s internal
structure and gravitational field. With
such an impressive trio preparing to ven-
ture to Venus, it’s safe to say we’ll unlock
some surprising secrets about our sister
world over the next decade or so.VENUS
STATS
Mass: 0.815 Earth masses
Diameter: 7,520 miles (12,100 km)
Surface temperature: 867 F (464 C)
Rotation period (day): 243 Earth days
(retrograde)
Orbital period (year): 225 Earth days
Moons: NoneVenus’ surface, usually shrouded by
the planet’s dense atmosphere,
bursts into view in this simulated-
color radar mosaic assembled
using data from the Magellan
spacecraft’s first mapping
campaign. Data from the Pioneer
Venus Orbiter were used to fill in
the gaps. NASA/JPL-CALTECHAncient lava flows and fractured
plains in the foreground extend
back more than 100 miles (200 km)
to Maat Mons along the southern
horizon in this computer-generated
3D view of the surface of Venus.
Maat Mons, an ancient and massive
shield volcano, is the second-tallest
mountain on Venus, peaking
some 3 miles (5 km) above its
surroundings. NASA/JPL-CALTECH