Howdy neighbour: NASA plans return to Venus

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After a gap of about three decades, NASA is finally looking at returning to our sister planet, Venus.

The last NASA probe to visit Venus was Magellan, which orbited the planet for four years as it mapped its surface features and then plunged into the atmosphere, sampling as it fell to destruction.

Venus has been visited by other robotic spacecraft in the past few years. Voyager passed by on its way out of the solar system, as did Messenger, Cassini and Galileo on their way to Mercury, Saturn and Jupiter, respectively.

Venus is conveniently situated to be used to give a gravity boost to spacecraft (and save fuel) to get to the other planets.

Venus has been visited by missions from the European Space Agency and Japan. Perhaps the most successful were probes from the U.S.S.R., which landed on the planet and got pictures before they were destroyed.

The planet has proven to be a difficult one to study. It is visible from Earth either before sunset or before sunrise. It is so bright that it even can be seen in the daytime, if you know where to look.


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While a beautiful object to look at, Venus is hardly the vacation spot of the solar system. We should not expect humans to visit the planet for a long time.

Venus has been described as Earth’s twin. It is about the same size as the Earth, but that is where any resemblance ends.

It is perpetually shrouded in clouds made of sulphuric acid. On its surface, the pressure of the atmosphere is about 90 times greater than we experience on Earth. And the atmosphere is so dense that looking through it is like looking through a liquid.

If that is not enough to take Venus off your vacation destination list, consider its surface temperature is 465 C. That’s hot enough to melt lead.

The temperature had been the greatest problem for Venusian landers. It is hard to get electronics that can survive these temperatures for long without melting.

Space probes have shown us that there is no liquid water on the planet, and the atmosphere is composed of mostly carbon dioxide, an infamous greenhouse gas. It is theorized that the CO2 trapped the solar radiation and resulted in a hellish planetary landscape.

So, if Earth and Venus are virtual twins, why did one become mankind’s home and the other a scene from Dante’s Inferno?

While we don’t know the answer, one theory suggests it has to do with the presence of liquid water on Earth. Much CO2 that comes from volcanoes into the atmosphere is readily absorbed and turned into rocks such as limestone. For this process to occur, the presence of liquid water is required.


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Without vast oceans, such as we have on Earth, the CO2 built up in Venus’s atmosphere and started a runaway greenhouse effect that dramatically increased the planet’s temperature.

NASA plans to send instruments to investigate the chemistry of Venus’s atmosphere, which will help in understanding the dynamics of the planet’s climate.

Another mission will use radar to map the planet in high resolution. This will allow us to see geological changes in the planet that will hint at modern-day volcanism and give clues into the history of Venus and how it evolved so differently from Earth.

Tim Philp has enjoyed science since he was old enough to read. Having worked in technical fields all his life, he shares his love of science with readers weekly. He can be reached by e-mail at:

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