[meteorite-list] Researchers Claim Planets Can Support Life Up To Ten Times Further Away From Stars Than Previously Thought

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 9 Jan 2014 16:45:18 -0800 (PST)
Message-ID: <201401100045.s0A0jIRw025584_at_zagami.jpl.nasa.gov>

http://www.dailymail.co.uk/sciencetech/article-2535900/Forget-Goldilocks-Zone-planets-support-life-TEN-times-away-stars-previously-thought.html

Forget the 'Goldilocks Zone' - planets can support life up to TEN times
further away from stars than previously thought

By Ellie Zolfagharifard
Mail Online
8 January 2014

Scientists may not have found extra-terrestrial life yet, but they now
claim there are far more aliens out there than first believed.

Researchers in Scotland believe that Earth-sized planets can support life
at least ten times further away from stars than previously thought.

This means that cold rocky planets previously considered uninhabitable
may be teeming with life beneath the surface.

Academics at the University of Aberdeen and University of St Andrews claim
the definition of the "Goldilocks" zone - the area of space around a
star, or sun, which can support life - is flawed.

They argue this definition fails to take into account life that can exist
beneath a planet's surface.

"As you get deeper below a planet's surface, the temperature increases,
and once you get down to a temperature where liquid water can exist -
life can exist there too," said Aberdeen University PhD student Sean McMahon.

-------------------------------
WHAT IS THE GOLDILOCKS ZONE?

The Goldilocks zone is the belt around a star where temperatures are ideal
for liquid water to pool on a planet's surface.

To determine the location of a star's habitable zone, scientists have
to first learn how much total radiation it emits.

Knowing precisely how far away a habitable zone needs to be from a star
also depends on chemistry.

For example, molecules in a planet's atmosphere will absorb a certain
amount of energy from starlight and radiate the rest back out.

How much of this energy is trapped can mean the difference between a turquoise
sea and erupting volcanoes.

Researchers in Scotland now claim that Earth-sized planets could support
life at least 10 times further away from stars than first thought.

-----------------------------

In a galaxy of 200 billion stars of various types, scientists estimate
there are 11 billion potentially habitable planets in the Goldilocks zone
as it is currently defined.

Factor smaller, dimmer red dwarf stars, and the number of planets with
mild temperatures similar to Earth rises to 40 billion.

Researchers in Aberdeen claim the figure is much higher. Mr McMahon told
MailOnline the number was "probably several times" larger but added that
the is difficult to quantify.

Mr McMahon's team created a computer model that estimates the temperature
below the surface of a planet of a given size, at a given distance from
its star.

"The deepest known life on Earth is 5.3 km below the surface, but there
may well be life even 10 km deep in places on Earth that haven't yet been
drilled," he said.

"Using our computer model we discovered that the habitable zone for an
Earth-like planet orbiting a sun-like star is about three times bigger
if we include the top five kilometres below the planet surface."

The model shows that liquid water could survive 5km below the Earth's
surface even if the Earth was three times further away from the sun.

"If we go deeper, and consider the top 10 km below the Earth's surface,
then the habitable zone for an Earth-like planet is 14 times wider," said
Mr McMahon.

The current habitable zone for our solar system extends out as far as
Mars, but this re-drawn habitable zone would see the zone extend out further
than Jupiter and Saturn.

The findings also suggest that many of the so-called "rogue" planets drifting
around in complete darkness could be harbouring life..

"Rocky planets a few times larger than the Earth could support liquid
water at about 5 km below the surface even in interstellar space, even
if they have no atmosphere because the larger the planet, the more heat
they generate internally," said Mr McMahon.

"It has been suggested that the planet Gliese 581 d, which is 20 light
years away from Earth in the constellation Libra, may be too cold for
liquid water at the surface.

"However, our model suggests that it is very likely to be able to support
liquid water less than 2 km below the surface, assuming it is Earth-like."

Another paper published by the same team suggests there could be more
life below the surface of the continents on Earth than there is below
the seafloor.

Mr McMahon hopes the studies will encourage other researchers to consider
how life on other planets might be detected.

"The surfaces of rocky planets and moons that we know of are nothing like
Earth," he said.

"They're typically cold and barren with no atmosphere or a very thin or
even corrosive atmosphere.

"Going below the surface protects you from a whole host of unpleasant
conditions on the surface. So the subsurface habitable zone may turn out
to be very important.

"Earth might even be unusual in having life on the surface."
Received on Thu 09 Jan 2014 07:45:18 PM PST