By: Leslie Mullen, Astrobiology Magazine
Published: 05/25/2013 09:25 AM EDT on SPACE.com
A Comparative Climatology Symposium held at NASA Headquarters on May 7 focused on new approaches to climate research by highlighting the similarities and contrasts between the environments of the rocky worlds Venus, Earth, Mars and Saturn’s smoggy moon Titan.
The symposium also included discussions about exoplanets, the sun and past, present and future space missions.
John Grunsfeld, Associate Administrator for NASA’s Science Mission Directorate, said that the upcoming James Webb Space Telescope will be able to make important observations of the atmospheres of exoplanets. [Photos: The James Webb Space Telescope]
He said JWST won’t be able to locate the exoplanets, only study them, but the recently selected TESS mission could act as a planet scout for JWST targets. It is estimated that TESS will discover around 300 "super-Earth" alien planets, many of them in the habitable zone.
But the number one challenge, Grunsfeld noted, is figuring out the climate of our own planet.
Understanding climate change
Jim Green, NASA’s Planetary Science Division Director, said that one goal is to examine a variety of planetary bodies as a system, to see if there are trends or similarities. He also pointed out that from a planetary scientist’s perspective, climate change on our planet is not a new thing.
"Earth’s climate has done nothing but change," Green said.
Green said that three Earth-observing satellites will be launched this year, and they will help us better understand how the climate is currently changing and the implications that has for our planet’s environment.
David Grinspoon, holder of the first Baruch S. Blumberg NASA/Library of Congress chair in Astrobiology, talked about Mars’ "ferocious and interesting" meteorology, and how Martian global dust storms may help unravel what happened on our planet during the K-T extinction 65 million years ago, when an asteroid hitting the Yucatan Peninsula is thought to have eradicated 75 percent of animals and plants on Earth, including the dinosaurs. [Wipeout: History's Most Mysterious Extinctions]
The 'Venus mafia'
As for Venus, Grinspoon said scientists believe current-day volcanism on Venus is thought to be necessary to sustain the planet’s thick clouds. He added that the active surface has eradicated most ancient rocks, preventing us from easily understanding Venus’ early history.
Grinspoon also discussed the unique climate of Titan, noting that the methane cycle on this moon of Saturn is "like Earth's hydrological cycle on steroids."
Studying the climates of Mars, Venus, Titan and even exoplanets could help us refine our climate models of the Earth. However, Grinspoon said that "clouds are the biggest uncertainty in understanding the past of Venus and predicting the future of Earth."
Tying climatology to astrobiology, Grinspoon said that our expectations of the other planets, in the absence of data, were that they'd be much more Earth-like than they actually are. We still haven’t found a planet quite like our own, although astronomers are zeroing in on exoplanets that should have habitable conditions.
But, Grinspoon said, "it may be that conditions for life's origin aren't rare, but the hard part is the persistence of habitable conditions."
Venus was a popular topic during the symposium. Roald Sagdeev, University of Maryland professor and former director of the Space Research Institute of the USSR Academy of Sciences, said during an overview of the Russian missions to Venus that "from the point of view of habitability, Venus is like having a dead body to study, which is of course very useful for learning anatomy."
David Crisp, Senior Research Scientist at the Jet Propulsion Laboratory/California Institute of Technology, said that sending weather balloons to Venus taught us a lot about atmospheric physics. And Roger Bonnet, Executive Director of the International Space Science Institute, said there was no chance for a big "flagship" mission to Venus, since the viewpoint among many amounts to "Who cares about clouds and wind on Venus, when we have so much of that on Earth? We want to see little green men!"
One participant noted the presence of "the Venus mafia" at the symposium, inferring that the focus on Earth’s "twin planet" had muscled out discussion of other places of interest.
But in addition to studies of Venus and other terrestrial worlds, there was a talk about our sun and its influence on space weather, and general discussions about refining climate models, defining habitable zones, and the importance of basic research.
The participants seemed to agree that, most importantly, planetary climate studies needed to be interdisciplinary, with scientists from different fields communicating and collaborating.
Michael Meyer, lead scientist for the Mars Exploration Program at NASA Headquarters, also pointed out that we should never become complacent in our scientific understanding. For instance, he said that while climate models have not been able to make early Mars warm enough to sustain liquid water on its surface, the same can be true for models of the young Earth.
And when it comes to understanding where a planet needs to reside in its solar system to be habitable — the so-called Goldilocks Zone where the temperature is just right for water to be liquid rather than ice or gas — he commented that "the approach [to the habitable zone] is very Goldilocks in that it's almost a fairy tale."
Finally, Meyer noted, just when we thought we understood how planets are made, we discovered hot Jupiters and other unusual exoplanets that "turned all of our planet formation models on their head."
"And that’s a good thing," he added.
The featured speakers at NASA's Comparative Climatology Symposium, titled "New Approaches to Climate Research," were John Grunsfeld, Jim Green, David Grinspoon, Lori Glaze, Mark Bullock, Roald Sagdeev, Jack Kaye, Lennart Bengtsson, David Crisp, Roger Bonnet, Mark Marley, and Madhulika Guhathakurta.
- How Mercury, Venus, Earth, And Mars Formed | Video
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Mercury has but a thin envelope of gas that barely qualifies as an atmosphere. The inexorable solar wind continually strips the planet of any gases that might be captured or retained by gravity. The tenuous atmosphere consists primarily of hydrogen making the atmosphere transparent to the darkness of space and the withering radiance of the nearby Sun. The solar wind interacts with the planet’s magnetic field to blast columns of dust and charged particles up into the atmosphere that then become a comet-like tail, evident as the sparkling haze shown in the upper atmosphere. The landscape is perforated with impact craters and covered in volcanic dust, similar to Earth's moon.
Due to its prolific volcanic activity, Venus is blanketed in an atmosphere of CO2 with clouds of sulfuric acid. This creates a yellowish envelope of hot, sulfurous air that obscures the NYC skyline and the nearby sun. The landscape is devoid of water and covered by craters, lava, sulfurous dust and other features created by Venus' volcanoes.
This is the original image of New York City that was used as the inspiration behind this slideshow.
Mars has an exceedingly thin and cold atmosphere composed primarily of CO2. Mars’ atmosphere has an oxidizing chemistry that converts the abundant iron materials on its surface into various forms of rust, evident as the tawny landscape. Strong convective currents in the atmosphere also stir up frequent dust storms that can cover vast expanses of the planet and last for months. The NYC skyline is thus caked in dust and framed in Mars' dusty red atmosphere.
Jupiter is the largest of the outer gas giant planets. Its atmosphere is so large and thick that the hydrogen and helium gas components condense into liquid and even metallic form near the base of the atmosphere. At around 100 km height above this liquid surface, the air has a similar air pressure to Earth’s atmosphere at the surface, but has a reducing chemistry that would burnish any metal surface, including that of the Statue of Liberty. The NYC skyline is depicted at this 100 km level, floating in the atmosphere.
Saturn has a similar atmosphere to that of Jupiter, containing a mixture of hydrogen and helium that condense at the base of the atmosphere. NYC is shown at about 100 km above this liquid surface, where the clear hydrogen resides at similar pressures to Earth’s atmosphere and contains soft cream colored clouds of ammonia ice with occasional thunderstorms (shown below the cloud deck). As with Jupiter, the atmospheric gases are highly reducing and would slowly dissolve any metal oxide surface like the green patina that covers the Statue of Liberty. White clouds of ammonia and light hydrocarbons float by above the skyline.
Uranus is a cold gas giant that rotates perpendicular to the plane of its orbit. It has very high wind speeds at certain latitudes due to the uneven heating of its surface. These winds are faster than the most powerful hurricane on Earth and would thus obliterate structures like the Statue of Liberty. The atmosphere is primarily composed of hydrogen and helium with occasional clouds of methane and bands of hydrocarbon haze, shown as the horse tail clouds above the skyline. The atmosphere also contains a considerable fraction of methane, giving the air a beautiful aquamarine tint.
Neptune is the outermost planet of the solar system and thus the darkest. Like the other gas giants it experiences extreme winds that would destroy buildings and other structures. Neptune's atmosphere consists primarily of hydrogen and helium with traces of ammonia and water giving it an azure tint. Ammonium and water ice condensate hangs as light colored cirro-stratus clouds above the skyline. Neptune’s atmosphere is the coldest place in the solar system.