NASA recently stunned planetary scientists when it announced
that it was going to send not one but two different spacecraft to Venus by the
end of the decade. On Thursday, the European Space Agency declared that it was
launching its own mission there: EnVision, an orbiter that would investigate
even more of the planet’s mysteries.
اضافة اعلان
Until this month, Venus had been somewhat lonely. NASA’s
last mission to the second planet was Magellan, which burned up in its skies in
1994. Europe’s last foray there was the Venus Express spacecraft, which orbited
the planet and studied it from 2006 until 2014. Today, Japan’s
climate-observing Akatsuki is the only emissary from Earth in orbit.
With Europe’s EnVision spacecraft added to NASA’s decision
to revisit Venus with the VERITAS and DAVINCI+ missions, it seems the next
decade will belong to Venus, and some in the Venusian science community have
been rendered speechless.
Upon hearing the news of the EnVision announcement, Martha
Gilmore, a planetary geologist at Wesleyan University, who is part of both the
DAVINCI+ and VERITAS teams, said: “I don’t even know what to do, my mind
can’t.” She paused and then added, “I’m in a weird state.”
“This is the best possible news,” said Paul Byrne, a
planetary scientist at North Carolina State University. “You couldn’t have
asked for a better situation.”
All three missions have different objectives and scientific
instruments. But each will contribute to addressing the same overarching
question. “Was Venus like Earth — was it habitable?” said Colin Wilson, a
planetary scientist at the University of Oxford and a deputy lead scientist on
EnVision.
Today, Venus is a post-apocalyptic wasteland: Its
asphyxiating carbon dioxide atmosphere mingles with highly corrosive sulfuric
acid clouds; its crushing surface pressures are equivalent to being 1 mile
underwater; and its surface temperatures hit 900 degrees Fahrenheit. Curiously
though, the presence of a rarer, heavier form of water in its atmosphere
indicates that there once was a lot more normal water on Venus.
If that water existed not as steam, but as lakes, rivers,
seas and oceans, it would have been the solar system’s second blue marble. How
did Earth escape Venus’ fate?
“Some of those answers lie on Earth, but some of them lie on
Venus,” Wilson said.
EnVision will study those mysteries with a suite of advanced
scientific instruments. Its radar systems will peer through Venus’ thick
atmosphere, mapping both the surface and the rocky layers up to 3,300 feet
below the surface. An array of spectrometers seeing in ultraviolet and infrared
light will analyze the atmosphere’s chemical composition, and differentiate
between types of rock on the ground. A radio science experiment will be able to
use slight changes in the planet’s gravity to parse the layer cake structure of
Venus’ geologic guts.
All of these instruments will help answer another major
query. “Is Venus alive or dead, geologically?” Wilson said.
Venus clearly had a geologically hyperactive past. Although
most scientists suspect that Venus is still erupting, the thick cloud cover has
prevented confirmation of that idea, just as it had prevented the search for
the telltale movement of faults.
As capable as these three missions are, they won’t solve all
of Venus’ mysteries, like whether phosphine, a gas potentially present in the
planet’s clouds, is being manufactured by microbial life.
But the hope is that this is the beginning of a second
Venusian renaissance. “It’s setting the stage for sustained Venus exploration,”
Byrne said, and only a prolonged series of missions to Venus — from more
orbiters and probes to atmospheric balloons and landers — will let us discover
why it became Earth’s evil twin.
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