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




EXO WORLDS
Can we find an ancient Earth-like planet with a dying biosphere?
by Amanda Doyle for Astrobiology Magazine
Moffet Field CA (NASA) Apr 23, 2015


The life cycle of a solar-like star shows how our Sun will expand into a red giant. Image courtesy ESO/M. Kornmesser. For a larger version of this image please go here.

Our Sun will evolve into a red giant star billions of years from now. The increased heat from the expanding Sun will scorch the Earth with dire effects to life. Climate models can be used to predict how this will happen, but, of course, this cannot be tested out on Earth.

Jack O'Malley-James of the Institute for Pale Blue Dots at Cornell University, along with colleagues, have been calculating the chances of discovering an old-Earth analog approaching the end of its habitable lifetime. This follows his work on Swansong Biospheres in which the potential bio-signatures of a dying world were assessed.

The new paper, "In Search of Future Earths: Assessing the possibility of finding Earth analogues in the later stages of their habitable lifetimes,"has been accepted for publication in the journal Astrobiology and is available in preprint.

The far future Earth
Searches are already in place to find Earth's twin, a planet with a similar mass and radius as the Earth and orbiting at the same distance as the Earth does from the Sun. However, finding an equivalent of Earth's much older cousin involves a different set of criteria.

The "habitable zone" is defined as the region where liquid water can exist on the surface of a planet. Habitable zones move outwards as a star ages, so a planet that was in the zone when the star was younger may not necessarily remain there.

An old Earth analogue is one that has been in the star's habitable zone for the entire main sequence lifetime of the star, known as the continuously habitable zone. As the purpose is to study planets in the final stages of habitability, a far future Earth would also have to be approaching the inner edge of the habitable zone.

As up to one-third of main sequence solar-like stars are thought to be in the later stages of their evolution, it is feasible that old Earth analogues could be detected. If any of these planets exist in the solar neighborhood, then they would be excellent candidates for future space telescopes with the capability to characterize a planet's atmosphere from its spectrum.

Searching nearby
There are six solar-like stars within 10 parsecs of the Sun that are old enough to harbor an old Earth analogue. A parsec is the equivalent of 3.26 light years. O'Malley-James calculated the location of the habitable zone for each star over its entire lifetime.

He then placed hypothetical planets in each system at a distance where the planet could remain habitable for billions of years. The temperature changes on the planet over the main sequence lifetime of the star can be modeled by comparing the predicted incoming and outgoing radiation.

The paper concludes that if Earth-like planets existed around these stars, then the one around 61 Vir would be at the right stage of its lifetime to be considered a far future Earth. Such a planet might be home to a declining microbial population, assuming that life evolved there in a similar manner to the Earth.

This hypothetical planet would be akin to the stage in future Earth's lifetime when the temperature has risen too high for complex life to survive, and microbes are the last lifeforms to cling to existence. Other stars could host planets similar to future Earth where only extremophile microbial life remains in a few select niches, however these biosignatures would be much more difficult to detect than the declining microbial biosphere.

A Galaxy Teeming with Earth-like Planets?
If an Earth-like planet existed around 61 Vir, it would provide a good opportunity to study the far future Earth. But what are the actual chances of such planets existing?

O'Malley-James used previous studies by other scientists in order to find out. One study, based on the number of planets found by NASA's Kepler mission, predicts that 8.6 percent of solar-like stars could harbor an Earth-like planet orbiting in the habitable zone.

A solar-like star is one that is of a similar temperature and mass as our own Star. There are 276 stars like our Sun within 100 parsecs, around half of which are older than six billion years. This means that there should be 11 potential targets.

However, another study showed that terrestrial planets are more likely to form less than one astronomical unit (AU, the distance between the Sun and the Earth) from the star. From the six example stars that O'Malley-James studied, the continuously habitable zone is located slightly further from the star than this. Combining these results indicates that there would actually only be one potential old-Earth analogue within the solar neighborhood.

"It turned out that these planets are probably not that common at all, so in reality any habitable planets in the 61 Vir system will probably not resemble an older version of Earth," said O'Malley-James. "This study highlights that finding replicas of our own world, in terms of the diversity and complexity of life, is going to be a much harder task than simply finding life."

Yet while there may only be one potential old-Earth analogue close enough to be studied in detail, there could still be thousands more in the distant reaches of our Galaxy.


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

.


Related Links
Astrobiology Magazine
Lands Beyond Beyond - extra solar planets - news and science
Life Beyond Earth






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 WORLDS
Spitzer Spots Planet Deep Within Our Galaxy
Pasadena CA (JPL) Apr 21, 2015
NASA's Spitzer Space Telescope has teamed up with a telescope on the ground to find a remote gas planet about 13,000 light-years away, making it one of the most distant planets known. The discovery demonstrates that Spitzer - from its unique perch in space - can be used to help solve the puzzle of how planets are distributed throughout our flat, spiral-shaped Milky Way galaxy. Are they con ... read more


EXO WORLDS
Dating the moon-forming impact event with meteorites

Yutu finds Moon still active in old age

Japan to land probe on the moon in 2018

Japan planning moon mission: space agency

EXO WORLDS
Robotic Arm Gets Busy on Rock Outcrop

Mars might have liquid water

NASA's Curiosity Rover Making Tracks and Observations

NASA Mars Rover's Weather Data Bolster Case for Brine

EXO WORLDS
Ramping Up For Johnson's Chamber A Test

Space icon reflects on origins of space program

Russia vows to put Russian cosmonauts on Moon no later than 2030

NASA Offers Study Volunteers Big Bucks to Stay in Bed

EXO WORLDS
Chinese scientists mull power station in space

China completes second test on new carrier rocket's power system

China's Yutu rover reveals Moon's "complex" geological history

China's Space Laboratory Still Cloaked

EXO WORLDS
Sixth SpaceX Delivery of Station Research With a Side of Caffeine

Research for One-Year Space Station Mission Launched On Falcon 9

Astronaut Hadfield to release first space album

Special 3-D delivery from space to Marshall Space Flight Center

EXO WORLDS
SpaceX Dragon cargo ship arrives at space station

Video shows SpaceX rocket booster crash land on floating target

Russia Should Consider Launching Super-Heavy Rockets From Vostochny

Rocket tips over after SpaceX recycle attempt

EXO WORLDS
Spitzer, OGLE spot planet deep within our galaxy

An exoplanet with an infernal atmosphere

White Dwarf May Have Shredded Passing Planet

Spitzer Spots Planet Deep Within Our Galaxy

EXO WORLDS
Disney develops layered fabric 3-D printer

How many gold atoms make gold metal?

Tethers Unlimited to recycle ISS plastic waste into 3D printer filament

Inventing a 2-D liquid




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.