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

When Life Went Global
by Johnny Bontemps for Astrobiology Magazine
Moffett Field CA (SPX) Jul 09, 2014

Artist's concept of lightning on Venus. Image courtesy ESA.

"An origin of life is not the same as an origin of a biosphere-that's an important distinction," says David Grinspoon, a planetary scientist and curator of astrobiology for the Denver Museum of Nature and Science.

To illustrate the concept Grinspoon offers a simple analogy. Say you're starting a camp fire. It's easy to get it to spark up, but you have to tend it first or it may just die out. But then the fire reaches a critical moment when it catches on and becomes self-sustaining. Now you can leave it alone, and go back to drinking beers.

Grinspoon wonders: Did life start out like little sparks that are vulnerable to extinction? And did it, once it transitioned to a global phenomenon, become like a self-sustaining flame?

False Start on Earth's Sisters?
Grinspoon's work focuses on the evolution of climate and atmosphere on Earth-like planets. At a recent conference themed Habitable Worlds Across Time and Space, held at the Space Telescope Science Institute in Baltimore, MD, he discussed the implications of this viewpoint for Earth's nearest neighbors: Venus and Mars.

The three rocky planets formed around the same time, some 4.5 billion years ago. Just like Earth, Venus and Mars may once have been watery worlds. Today they seem dry and barren, but several lines of evidence suggest they both had oceans in their early days.

"Everything we know about them points to an early environment that was hospitable for life," Grinspoon says in an interview with Astrobiology Magazine.

Somehow only Earth held onto its water, and eventually burst out with the self-sustaining fire of life.

"Maybe what's rare is not the formation of watery planets, but the persistence of habitable environments over cosmological timescales," he says.

By the end of his talk, titled "Venus and Mars as Failed Biospheres," Grinspoon raises an intriguing question. Is a biosphere necessary for the long-term survival of life?

The Turning Point on Earth
The oldest signs of life on Earth date to about 3.5 billion years ago. But when did our planet transition from having organisms to having a biosphere?

"It's hard to tell-it's something that hasn't been studied enough," Grinspoon says. "But my guess is that once life has some kind of global influence, then you're transitioning to a biosphere."

To him the shift had likely occurred by 2.3 billion years ago, or around the time photosynthetic microbes began churning out oxygen into Earth's oceans and atmosphere, affecting life's survival everywhere on the planet.

However, life's influence went way beyond its power to shape the Earth's atmosphere. According to recent studies, life has shaped everything from Earth's interior to the diversity of minerals on its surface. As Grinspoon puts it, "Life has got Earth in its clutches in this deep, and not always obvious way."

Birth of a Living World
"Can a planet, in a sense, become alive?" Grinspoon asks.

It's not the first time he puts the concept forward. In his 2003 book Lonely Planets, Grinspoon introduced the "Living World" hypothesis, a slight variant the well-known Gaia hypothesis.

In the 1970s, the chemist James Lovelock and the biologist Lynn Margulis developed the idea that our Earth may be like a living organism, a self-regulating entity that employs feedback loops to keep conditions just right for life. They christened the potentially living planet "Gaia," from the Greek for Mother Earth.

The idea has since been hotly debated, mostly pegged as more philosophical than scientific. Still, many researchers agree that the concept has helped Earth system science move forward, allowing us to realize that many of Earth's cycles-the water, nitrogen, and carbon cycles; plate tectonics; and the climate-are deeply interconnected, and is modulating and being modulated by life on Earth.

"Gaia may just be a nice metaphor," Grinpsoon says, "but I wonder if it may be fruitful to think of life as something that happens not just on a planet, but as something that happens to a planet."

"You cannot easily separate the living and the non-living parts of Earth," he adds. "Life has made Earth the way it is to a large extent. That's the general meaning of the Gaia hypothesis, and the Living Worlds hypothesis is simply extending the idea to other planets."

Finding Life's Elsewhere
"The idea of an origin of life separated from the birth of a living world has interesting implications for life elsewhere," Grinspoon writes in Lonely Planets.

"If self-regulating Gaia is responsible for Earth's life longevity, then we need to find other places where this kind of global organism has evolved, not merely places where the origin of life might once have occurred."

In other words, our search for life should then target places with active geological and meteorological cycles, the potential tell-tales of a vibrant biosphere.

We've now found nearly 2,000 planets orbiting distant stars, and counting. While these worlds may be too far for us to find any direct evidence for life in the near future, researchers are becoming increasingly proficient at making out the composition of their atmosphere. That ability could perhaps one day allow us to distinguish between "failed biospheres" and potentially living worlds.

In the meantime, a Living World perspective may yield useful insights as we target our search for life closer to home, in our own solar system. Jupiter's icy moon, Europa, seems to have a young and active surface, while Saturn's moon, Titan, is meteorologically well-alive with methane raining down and filling rivers and lakes.

Even our closest neighbor, Venus, long viewed as a hellish world with its extreme heat, crushing pressure, and clouds of sulfuric acid, could potentially host some kind of life, if vigorous cycles are any indicators of a healthy biosphere, as Grinspoon argued in his 1997 book, Venus Revealed.

For Mars it would be a different story, with its stale atmosphere of carbon dioxide and its rusty, quiet surface.

"From a living worlds perspective, the new wave of interest in life on Mars is highly questionable," Grinspoon wrote in Lonely Planets.

But even if Mars seems dead now, it may not be the end of it for the Red Planet. By 2030, the mission "Mars One" will aim to establish the first human settlement. In the end, the "fire" which started on Earth 3.5 billion years ago could soon leap and catch on elsewhere.


Related Links
Astrobiology Magazine
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 DiggDigg RedditReddit GoogleGoogle

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

Two 'Goldilocks planets' that might support life are proven false
University Park PA (SPX) Jul 04, 2014
Mysteries about controversial signals coming from a dwarf star considered to be a prime target in the search for extraterrestrial life now have been solved in research led by scientists at Penn State University. The scientists have proven, for the first time, that some of the signals, which were suspected to be coming from two planets orbiting the star at a distance where liquid water coul ... read more

NASA LRO's Moon As Art Collection Is Revealed

Solar photons drive water off the moon

55-year old dark side of the moon mystery solved

New evidence supporting moon formation via collision of 2 planets

Rover Uses Arm to Study Several Rocks and Takes Panoramic Images

ADS complete heat shields for 2016 ExoMars mission

Martian salts must touch ice to make liquid water

First LDSD Test Flight a Success

Sun Sends More 'Tsunami Waves' to Voyager 1

Privately funded solar spacecraft to launch in 2016

Space Launch System Core Stage Passes Critical Design Review

Taiwan's tourism revenue hits record high in 2013

Chinese moon rover designer shooting for Mars

Yutu designer's bittersweet

Are China's Astronauts Moonbound

Chinese scientists prepare for lunar base life support system

Orbital Targets July 11 For ISS Commercial Resupply Mission

Space junk damages ISS US segment

NASA Television Coverage Set for Orbital-2 Mission to Space Station

Spot the Space Station looking at you

RUAG Space wins major Ariane 5 payload fairing contract

Final ATV loaded with cargo after integration on Ariane 5

Russia Launches Rokot Carrier Rocket with Three Satellites

Eco-Friendly 'Angara' Rocket Installed On Plesetsk Launch Pad

Newfound Frozen World Orbits in Binary Star System

Discovery expands search for Earth-like planets

Astronomers discover most Earth-like of all exoplanets

Mega-Earth in Draco Smashes Notions of Planetary Formation

ASC Signal Introduces Innovative Carbon-Fiber Antenna

Resolve Supplies Zoom Lenses for NASA Testing

With 'ribbons' of graphene, width matters

Even geckos can lose their grip

The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news 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 All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.