Fifty years ago on Dec. 14, NASA’s Mariner 2 spacecraft made its
closest approach to the planet Venus, marking the first-ever flyby of
another planet.
Mariner 2 zoomed to within 21,564 miles (34,675 kilometers) of Venus on
Dec. 14, 1962, gathering a trove of data about Earth’s hellishly hot
sister planet. The probe took the first close-up measurements of Venus’
scorching temperatures, for example, helping confirm scientists’
suspicions that a runaway greenhouse effect had taken hold of the world.
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Tracking Mariner 2′s radio signals, researchers also calculated Venus’ mass with unprecedented precision, NASA officials said.
The spacecraft’s flyby also marked a proud moment for NASA and the
United States, after a five-year stretch in which the Soviet Union had
claimed all of the world’s big space firsts.
The Soviets successfully launched the first artificial satellite in
1957, sent a probe to the moon in 1959 and put the first human in space
in 1961.
“JPL has always attempted to do mighty things on behalf of NASA and our nation,” Charles Elachi, director of NASA’s Jet Propulsion Laboratory in
Pasadena, Calif., which managed Mariner 2′s mission, said in a
statement. “Achieving America’s first ‘first in space’ is among the
lab’s proudest achievements.”
Mariner 2 had a bumpy ride. Shortly after launch on Aug. 27, 1962, an
electrical short caused the probe’s rocket to roll, rendering it
unresponsive to guidance commands. But the short circuit mysteriously
healed itself about a minute later, NASA officials said.
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Things got dicey during Mariner 2′s cruise to Venus, too. A solar panel
on the spacecraft stopped working on two separate occasions, and
attitude-controlling gyroscopes misbehaved. Further, the probe’s
temperature rose dramatically as it approached Venus, causing managers
to worry that Mariner 2 might be cooked before it could complete its
mission.
But Mariner 2 overcame all of this, and the rest is history. In
addition to lifting Venus’ veil, the spacecraft’s observations also
confirmed the existence of the solar wind and enabled scientists to
refine the value of the astronomical unit — the distance from Earth to
the sun, which is about 93 million miles (150 million km).
In the half-century after Mariner 2′s close encounter, other spacecraft
have further studied the second planet from the sun. The Soviet Union
even landed a number of probes on Venus’ surface, beginning with Venera 7
in 1970. But Mariner 2 will always have a special place in history.
“There will be other missions to Venus, but there will never be another
first mission to Venus,” Jack James of JPL, Mariner 2′s project
manager, said before his death in 2001.
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