Scientific American - February 2019

58 Scientific American, February 2019

PRECEDING PAGES: NASA AND JPL

Shortly afterward, though, scientists cobbled to -

geth er plans for a bargain-priced spacecraft ($680

million) made of leftover hardware and, miraculously,

saved the mission. In 1989 the Magellan orbiter launched

on a reconnaissance mission to Venus, and by 1990 it

was in orbit. Over the next five years the orbiter

returned near-global radar images, gravity data and a

topographic map of the second planet from the sun. It

was the latest in a long line of Soviet and U.S. missions

to our neighboring planet, but when Magellan

plunged to Venus’s surface in 1994, NASA’s support for

Venus spacecraft died with it. Since then, scientists

have submitted more than 25 proposals for return

missions to Venus, and although some of those

received high rankings from review boards, none were

approved. Decades-old data gathered by Magellan re-

main the foundation of Venus geoscience to this day.

But planetary scientists never give up, and we have

made progress in uncovering the secrets of this world

nonetheless. Since Magellan, the European and Japa-

nese space agencies have sent successful missions to

Venus, leading to breakthroughs in understanding its

atmosphere. Meanwhile scientists have been busy

rewriting the textbooks on our sister planet by per-

forming new analyses of Magellan data. We now think

that volcanoes are rampant on Venus, and we have

even found hints of the start of plate tectonics, which

scientists think is critical for a planet’s habitability.

New theoretical models also suggest Venus may have

had liquid water on its surface until relatively late in

its history—meaning that it may have been hospitable

to life much longer than we once thought.

N 1982 ALL ANYONE COULD TALK ABOUT IN THE PLANETARY SCIENCE DEPARTMENT AT THE

Massachusetts Institute of Technology was the cancellation of NASA’s latest flagship mis-

sion, the Venus Orbital Imaging Radar (VOIR). One of us (Dyar) was a graduate student

there at the time. (The other two were still in college and elementary school.) Graduate

students wept openly in the hallways, and veteran faculty shook their heads. The newly

elected Reagan administration had enacted sweeping cuts to space exploration, and VOIR

was one of the casualties.

M. Darby Dyar is a mineral spectroscopist who studies extraterrestrial

minerals and glasses from the moon, Mars, comets and asteroids.

She is a senior scientist at the Planetary Science Institute and Kennedy-

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Suzanne E. Smrekar ÒÜæf”rÒܐrf”|rÍr§Ür諛æܔ«§DÍëμDܐÒ

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of the InSight Mission at NASA’s Jet Propulsion Laboratory,

where the mountain biking is awesome.

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Stephen R. Kane is a planetary astrophysicist who has

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IN BRIEF

Venus and Ear th started out much the same,

but at some point, the planets diverged. Earth

went on to host oceans and an atmosphere.

Venus’s surface, meanwhile, became inhospitable

to life. Yet our neighboring planet still has active

volcanism and hints of nascent plate tectonics.

Learning why Venus evolved the way it did could illu-

minate the possibilities for life on the many Venus- like

exoplanets out there. A new mission to Venus is needed.

© 2019 Scientific American