Sky and Telescope - September 2018 - 19

INFOG R A PHIC: TERRI DUBÉ / S&T; PA NCA K E DO ME BACKG ROUND: N ASA /JPL; 3D V ENUS: N ASA /JPL;
A K ATSUK I IM AG ES: JA X A / ISAS / DA RTS / DA MIA BOUIC CC BY-NC -SA 3.0

But while NASA's planetary-science community is thankful that its international partners have picked up the baton,
many say it is not enough. They want to send orbiters that
will map the world in closer detail. They want to send balloons that will fly into those acidic clouds to test for stable
isotopes and noble gases, which bear the fingerprints of
Venus's origin and evolution. And they want to drop probes
onto its surface, landing on some fresh lava flows or the tesserae - regions of crumpled terrain with unknown origins
- in order to better assess the past
habitability of our sister planet.
With such lofty goals, scientists
have written one mission proposal
after the next, only to watch NASA
reject them time and time again.
"It's like Lucy holding the football
for Charlie Brown," says Darby
Dyar (Mount Holyoke College).
p IN ULTRAVIOLET This
"We run and we run and we try
two-image composite from
to kick the damn ball and it gets
Akatsuki data shows clouds
pulled out from under us."
and hazes (65 to 75 km altiThat isn't to say that Venus
tude). Colors track changes
scientists
don't recognize the merit
in sulfur dioxide and an
unknown UV absorber.
of other missions. "I look at the
missions that have been selected
over the last couple of rounds, and they're all outstanding,"
Glaze says. "They have great science ideas. They're all going to
produce compelling discoveries." But she admits she's also a
bit frustrated. "I do feel that it's time for Venus to play a role
in this whole planetary evolution story."
Others are more dismal. Without a dedicated mission,
some argue, the group of Venus scientists will shrink. And
that will mean that there are even fewer scientists who will
advocate for new missions. It will also mean that NASA might
soon find itself devoid of anyone who has actually sent a
probe to Venus. There is simply so much to gain from a Venus
mission and so much to lose without one.

The Martian Allure
So what's behind NASA's long hiatus? The one to ask is
Thomas Zurbuchen, NASA's Associate Administrator for the
Science Mission Directorate. He's guided by a once-per-decade
survey of planetary scientists that ranks funding priorities
and future exploration candidates - and which, notably,
ranked placing a spacecraft on Venus's surface below a Mars
sample-return effort and a mission to the subsurface-oceanbearing Europa. But ultimately, he's the person who chooses
the interplanetary missions that fly and those that won't. And
he does so based on three criteria: "The science is excellent,
the technology is ready to go, and sometimes you need a little
bit of luck, too," he says. Not that it's an easy decision. "It's
one of the hardest things you'll ever do," he adds.
Zurbuchen has profound empathy for those who don't see
their projects accepted. "Every time I lost a proposal I took it
personally - deeply personally," he says. "I think that's what

we're seeing. It's just researchers who really care about what
they do, and they bring passion to the table every day."
Green agrees. Several years ago, NASA rejected his own
mission proposal, causing his sunny demeanor to take a
downward swing. "I was depressed for six months," he says.
"That's what happens in this field. It's not easy."
But most Venus researchers argue there are deeper issues
at work. Although every planetary scientist has a pet theory
- which together shed more light on human nature than on
our sister planet - all agree that the dogged search for extraterrestrial life helped shift NASA's gaze away from Venus and
toward Mars. In fact, Magellan's discovery just might be what
sealed Venus's exploratory fate: Once NASA managers realized that Venus's young lava flows likely covered any evidence
of past life or liquid water, they left the toxic world behind
and turned their focus toward the Red Planet.
"Mars has this glitter to it," says Mark Marley (NASA
Ames). That much could be seen in 1996 when scientists
announced the discovery of what looked like bacteria fossilized within the Allan Hills 84001 meteorite - a rock that

"It's quite possible that Venus is
actually the end-state of all terrestrial
planets." -Stephen Kane

blasted off Mars and landed on Earth. Although scientists
now almost universally dismiss a biologic origin for the
meteorite's microscopic structures, the excitement it helped
feed persisted. Exploring Mars's dusty red surface could help
scientists answer one of the greatest questions they have ever
asked: Is there life beyond Earth? The temptation was impossible to resist.
And it remains impossible to resist. Even as NASA pushes
outward to other bodies in the solar system (and beyond), the
q VENUS IN 3D Colored based on images from the Soviet Venera 13 and
14 landers, this simulated perspective of Magellan data looks down on Sapas Mons, an equatorial shield volcano on the western edge of Atla Regio.
The volcano is 1.5 km tall. Lava flows extend for hundreds of kilometers
across the foreground plains, and Maat Mons lies on the horizon. The
vertical scale in this perspective is exaggerated by a factor of 10.

sk yandtelescope.com * S E P TE M B E R 2 018

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Table of Contents for the Digital Edition of Sky and Telescope - September 2018

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