Subscribe free to our newsletters via your
. 24/7 Space News .




EXO LIFE
Using Planet Colors To Search For Alien Earths
by Staff Writers
Pasadena CA (JPL) Nov 03, 2010


NASA researchers analyzed the light reflected by the planets and plotted the results on a "color-color" diagram. By plotting the ratios of red to green light as well as blue to green, the planets cluster into "color families." On the diagram, Earth is easily distinguishable from the other major planets. Credit: NASA/GSFC

Earth is invitingly blue. Mars is angry red. Venus is brilliant white. Astronomers have learned that a planet's "true colors" can reveal important details. For example, Mars is red because its soil contains rusty red stuff called iron oxide. And the famous tint of our planet, the "blue marble"? It's because the atmosphere scatters blue light rays more strongly than red ones. Therefore the atmosphere looks blue from above and below.

Planets around other stars probably exhibit a rainbow of colors every bit as diverse as those in our solar system. And astronomers would like to eventually harness color to learn more about exoplanets. Are they rocky or gaseous - or earthlike?

In a study recently accepted for publication in The Astrophysical Journal, a team led by NASA astronomer Lucy McFadden and UCLA graduate student Carolyn Crow describe a simple way to distinguish between the planets of our solar system based on color information. Earth, in particular, stands out clearly among the planets, like a blue jay in a flock of seagulls.

"The method we developed separates the planets out," Crow says. "It makes Earth look unique."

This suggests that someday, when we have the technology to gather light from individual exoplanets, astronomers could use color information to identify earthlike worlds. "Eventually, as telescopes get bigger, there will be the light-gathering power to look at the colors of planets around other stars," McFadden says. "Their colors will tell us which ones to study in more detail."

Earth the Exoplanet
The project began in 2008, when Crow teamed up with McFadden, her faculty mentor at the University of Maryland in College Park. McFadden currently heads university and post-doctoral programs at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

New color information about Earth, the moon, and Mars became available, thanks to NASA's Deep Impact spacecraft. En route to a planned encounter this November with Comet 103P/Hartley 2, Deep Impact observed Earth.

The idea was to determine what our home looks like to alien astronomers and eventually use that insight to figure out how to spot earthlike worlds around other stars.

As Deep Impact cruised through space, its High Resolution Instrument (HRI) measured the intensity of Earth's light. HRI is an 11.8-inch (30 cm) telescope that feeds light through seven different color filters mounted on a revolving wheel.

Each filter samples the incoming light at a different portion of the visible-light spectrum, from ultraviolet and blue to red and near-infrared. On May 28, 2008, Deep Impact even caught a glimpse of the moon's light as it crossed in front of Earth. Later, in 2009, HRI scoped Mars.

McFadden wondered what combination of color information from the filters would best distinguish Earth from the other planets and moons of the solar system. She recruited Crow to work on the project. Eight other researchers from NASA, the University of Maryland, the University of Washington (Seattle), and the Johns Hopkins University Applied Physics Lab also joined the team.

The Magic Mix
The Deep Impact color data covered Earth, the moon, and Mars. The relative amounts of light passing through the filters vary for each planet or moon, providing a kind of color fingerprint. To this the team added existing color information about Mercury, Venus, Jupiter, Saturn, Uranus, Neptune, and Saturn's moon Titan.

A simple side-by-side comparison of color data on all the major planets was a confusing mess. The team finally found a combination of three different filters - one in the blue, one in the green, and one in the red - that highlights the differences between the planets.

On a special "color-color" diagram the team created, the planets cluster into groups based on similarities in the wavelengths of sunlight that their surfaces and atmospheres reflect. The gas giants Jupiter and Saturn huddle in one corner, Uranus and Neptune in a different one. The rocky inner planets Mars, Venus, and Mercury cluster off in their own corner of "color space."

But Earth is the true loner in color space. Its uniqueness traces to two factors. One is the scattering of blue light by the atmosphere. This is called Rayleigh scattering, after the English scientist who discovered it.

The other reason Earth stands out in color space is because it does not absorb a lot of infrared light. That's because our atmosphere is low in infrared-absorbing gases like methane and ammonia, compared to the gas giant planets Jupiter and Saturn.

"It is Earth's atmosphere that dominates the colors of Earth," Crow says. "It's the scattering of light in the ultraviolet and the absence of absorption in the infrared."

Colorful Future
Someday, the three-filter approach may provide a rough "first cut" look at exoplanet surfaces and atmospheres. "There are some things we can tell from the colors but there are some things that we can't quite tell without additional information," Crow says.

For example, if an exoplanet shows a similar color fingerprint to Earth's, it would not necessarily mean that the planet has the blue skies and vast oceans of our home. But it would tell us to look at that planet more closely.

And that would be an important first step toward making sense of the colorful complexity of the 490 (and counting) alien planets already discovered, and the scores more on the way.

.


Related Links
EPOXI at NASA
EPOXI at UMD
Life Beyond Earth
Lands Beyond Beyond - extra solar planets - news and science






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





EXO LIFE
Energy Revolution Key To Complex Life
London, UK (SPX) Oct 29, 2010
The evolution of complex life is strictly dependent on mitochondria, the tiny power stations found in all complex cells, according to a new study by Dr Nick Lane, from the University College London and Dr William Martin, from the University of Dusseldorf. "The underlying principles are universal. Energy is vital, even in the realm of evolutionary inventions," said Dr Lane, UCL Department o ... read more


EXO LIFE
New type of moon rock identified

Moon Express Enters $30 Million Google Lunar X PRIZE Competition

Dead Spacecraft Walking

Surviving Lunar Dangers

EXO LIFE
Mars Rovers Mission Using Cloud Computing

Mars Volcanic Deposit Tells Of Warm And Wet Environment

Opportunity Keeps On Driving To Endeavour Crater

Ancient Mars Was Wet, Cozy And Life Friendly

EXO LIFE
The Fading Final Frontier

Astronauts4Hire Offers Limited Time High Profile Sponsorship Special

Pioneering Science And The D1 Spacelab Mission

Interstellar Voyage Continues With New Project Manager

EXO LIFE
China Goes To Mars

China says manned space station possible around 2020

China Kicks Off Manned Space Station Program

NASA chief says pleased with 'comprehensive' China visit

EXO LIFE
Progress Docks On Auto

Cargo vessel links up with ISS after auto-docking problem

NASA Seeks More Proposals On Commercial Crew Development

EU mulls opening ISS to more countries

EXO LIFE
Ariane 5 Lofts Dual Birds

Payload Preparations Underway For Fifth Ariane 5 2010 Mission

Sea Launch Company Emerges From Chapter 11

Ariane 5 Rolls Out For Dual Bird Launch

EXO LIFE
e2v To Develop Image Sensors For PLATO Exoplanet Mission

Solar Systems Like Ours May Be Common

Astronomer Greg Laughlin To Talk About Earth-Like Planets

NASA Survey Suggests Earth-Sized Planets are Common

EXO LIFE
Samsung aims to sell 1 million Galaxy Tabs by year's end

Holographic video takes step forward with updated display

Facebook steps into middle of smartphone lifestyles

Space Fence Program Completes Critical Milestone




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement