Saturday, December 20, 2014

ANOTHER EARTH: NASA's Venus "Cloud" Mission - "Did It Once Have Ancient Oceans"?

via NASA's Goddard Space Flight Center and ESA


December 20, 2014 -  SPACE
 - The conditions on Venus are hard to describe. Many planetary scientists say "Start by imagining Hell and work up from there." It's an environment where words like "over 500 degrees Celsius" get thrown around, and it's flat-out crushed every probe we've sent into it. Even worse, there's almost no water.

But recently, NASA's Langeley Research Center has proposed a High Altitude Venus Operational Concept (or HAVOC), the proposed space balloons would sit at roughly 50 kilometers above Venus, with astronauts living in a cloud city, subject to about 85% Earth gravity, and the temperature peaks below 80°C — still higher than you could find anywhere on Earth, but low enough that NASA scientists can deal with it via the super-materials of modern astrophysics. On average, Venus is less than half Mars’ distance from Earth, while its thick atmosphere would both protect astronauts from intense radiation and allow enough solar radiation through to make solar power a real option. The Langeley team argues that we ought to focus on the upper atmosphere of Venus, and not the surface of Mars, for our first manned mission to an alien world.

The Venus mission would occur in five stages: robotic exploration, a 1-month orbiting mission, a 1-month atmospheric mission, a 1-year atmospheric mission, and finally a semi-permanent installation with rotating crew. This would be far easier to keep going than a Mars missions since, first of all, it’s so much closer, and since docking with a cloud facility wouldn’t require as much fuel/power as landing and taking off from the surface of Mars.

Venus was created at about the same time as Earth, in about the same place, and it's roughly the same size - it would therefore have started with the same materials as us, drawn together from the same region of the planet forming dust left over from the sun. But Venus now has only 0.001% of our water content, and a couple of flybys by the Venus Express may have revealed the reason.

In 2008, the probe discovered hydrogen and oxygen streaming off the night side of the planet in a 2:1 ratio, which you might recognize as the ratio in H20. It seems that what little water Venus has left is being blasted apart in the atmosphere by the solar wind, a vast stream of charged particles blown out by the sun. Venus Express has passed by the dayside and measured almost three hundred kilograms of hydrogen a day being lost into space. It hasn't found any oxygen yet, but the search continues.

"Venus today has a thick atmosphere that contains very little water, but we think the planet started out with an ocean's worth of water," said John T. Clarke of Boston University.

Scientists are still trying to determine whether water existed on the surface of Venus or only high up the atmosphere, where temperatures were cooler. If the surface temperature stayed below the boiling point of water long enough, rivers might have once flowed on the planet. Venus may have even had ice.

The key to figuring out how much water Venus once had lies in how much hydrogen and deuterium, a heavier version of hydrogen, remain in the atmosphere. Both can combine with oxygen to make water, either in the familiar H2O form or the rarer hydrogen, deuterium and oxygen form, called HDO. (Very small amounts of D2O also form.)

Intense UV light from the sun has broken apart nearly all of the water molecules in Venus' atmosphere. Because the regular hydrogen atoms in the water are lighter, they escape into space more quickly than the heavier deuterium ones. By comparing the amount of deuterium now in the atmosphereto the amount of hydrogen, researchers can estimate how much water disappeared from Venus and how quickly it happened.

Early estimates, made from data collected by NASA's 1978 Pioneer Venus spacecraft and other observations, indicated Venus could have had enough ancient water to cover the whole globe with 23 feet (7 meters) of liquid. But it turns out that the amounts of hydrogen and deuterium can vary at different heights in Venus' atmosphere, which could change the calculations.

Data gathered from European Space Agency’s Venus Express is invaluable to climate scientists modeling Earth’s climate to predict its future. The climate of our two neighbors is in stark contrast to Earth with Venus is a cloudy inferno and Mars is a frigid desert.

Astrobiologist David Grinspoon believes that scientists should look at our neighboring planets to help understand the perils of global warming. “It seems that both Mars and Venus started out much more like Earth and then changed. They both hold priceless climate information for Earth."

Climate scientists believe that Venus experienced a runaway greenhouse effect as the Sun gradually heated up. Astronomers believe that the young Sun was dimmer than the present-day Sun by 30 percent. Over the last 4 thousand million years, it has gradually brightened. During this increase, Venus’s surface water evaporated and entered the atmosphere.

“Water vapor is a powerful greenhouse gas and it caused the planet to heat-up even more. This is turn caused more water to evaporate and led to a powerful positive feedback response known as the runaway greenhouse effect,” says Grinspoon.

As Earth warms in response to manmade greenhouse gases, it risks the same fate. Reconstructing the climate of the past on Venus can give scientists a better understanding of how close our planet is to such a catastrophe. However, determining when Venus passed the point of no return is not easy. Maybe that's where a NASA HAVOC mission come is. - Daily Galaxy.

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