Stephen Hawking: Wake Up, Science Deniers! --"Earth is Morphing into Venus" (WATCH Today's 'Galaxy' Stream)
"Venus is like Earth in so many ways," explains Stephen Hawking. "A sort of kissing cousin. She's almost the same size as Earth, a touch closer to the Sun. And, she has an atmosphere that could crush a submarine."
In the second episode of the original documentary series Stephen Hawking's Favorite Places, the renowned physicist proposes that climate-science deniers take a trip to Venus, even offering to pay for their fare to view the ultimate results of their ignorance. The conditions on Venus today, Hawking says, are almost impossible to comprehend. Planetary scientists say "start by imagining Hell and work up from there." At the surface, Venus roasts at more than 800 degrees Fahrenheit under a suffocating blanket of sulfuric acid clouds and a crushing atmosphere more than 90 times the pressure of Earth's that has flat-out crushed every probe we've sent to it.
In the findings of a study conducted by the National Aeronautics and Space Administration (NASA) in 2002, it was suggested that Venus shared similar traits to the Earth and even had water around 4.5 billion years ago. However, as the planet increasingly warmed, more water vapor was in its atmosphere resulting to more heat being trapped which continued until its oceans completely evaporated.
Using rudimentary computer-generated imagery (CGI), Hawking can be seen traveling in a spaceship to Venus as he passed through clouds of sulfuric acid. However, he finds that the pressure on the planet is roughly 90 times that of the Earth "enough to crush a submarine," while the temperature is around 200 degrees. He explains that the Earth could find itself in a similar situation if greenhouse gases are not controlled.
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 atmosphere to 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 entire planet 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.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 trivial.
The Daily Galaxy via NASA's Goddard Space Flight Center and ESA
Image credit top of page: NASA/Getty Images