Most liveable alien worlds ranked

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Gaborn

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Scientists have outlined which moons and planets are most likely to harbour extra-terrestrial life.

Among the most habitable alien worlds were Saturn's moon Titan and the exoplanet Gliese 581g - thought to reside some 20.5 light-years away in the constellation Libra.

The international team devised two rating systems to assess the probability of hosting alien life.

They have published their results in the journal Astrobiology.

In their paper, the authors propose two different indices: an Earth Similarity Index (ESI) and a Planetary Habitability Index (PHI).

"The first question is whether Earth-like conditions can be found on other worlds, since we know empirically that those conditions could harbour life," said co-author Dr Dirk Schulze-Makuch from Washington State University, US.

"The second question is whether conditions exist on exoplanets that suggest the possibility of other forms of life, whether known to us or not."

As the name suggests, the ESI rates planets and moons on how Earth-like they are, taking into account such factors as size, density and distance from the parent star.

The PHI looks at a different set of factors, such as whether the world has a rocky or frozen surface, whether it has an atmosphere or a magnetic field.

It also considers the energy available to any organisms, either through light from a parent star or via a process called tidal flexing, in which gravitational interactions with another object can heat a planet or moon internally.

And finally, the PHI takes into account chemistry - such as whether organic compounds are present - and whether liquid solvents might be available for vital chemical reactions.

The maximum value for the Earth Similarity Index was 1.00 - for Earth, unsurprisingly. The highest scores beyond our solar system were for Gliese 581g (whose existence is doubted by some astronomers), with 0.89, and another exoplanet orbiting the same star - Gliese 581d, with an ESI value of 0.74.

The Gliese 581 system has been well studied by astronomers and comprises four - possibly five - planets orbiting a red dwarf star.

HD 69830 d, a Neptune-sized exoplanet orbiting a different star in the constellation Puppis, also scored highly (0.60). It is thought to lie in the so-called Goldilocks Zone - the region around its parent star where surface temperatures are neither too hot nor too cold for life.

The highly rated worlds from our own solar system were Mars, with a value of 0.70, and Mercury, with 0.60.

The Planet Habitability Index produced different results. The top finisher here was Saturn's moon Titan, which scored 0.64, followed by Mars (0.59) and Jupiter's moon Europa (0.47), which is thought to host a susbsurface water ocean heated by tidal flexing.

The highest scoring exoplanets were, again Gliese 581g (0.49) and Gliese 581d (0.43).

In recent years, the search for potentially habitable planets outside our solar system has stepped up several gears. Nasa's Kepler space telescope, launched into orbit in 2009, has found more than 1,000 candidate planets so far.

Future telescopes may even be able to detect so-called biomarkers in the light emitted by distant planets, such as the presence of chlorophyll, a key pigment in plants.
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EARTH SIMILARITY INDEX

Earth - 1.00
Gliese 581g - 0.89
Gliese 581d - 0.74
Gliese 581c - 0.70
Mars - 0.70
Mercury - 0.60
HD 69830 d - 0.60
55 Cnc c - 0.56
Moon - 0.56
Gliese 581e - 0.53
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PLANET HABITABILITY INDEX

Titan - 0.64
Mars - 0.59
Europa - 0.49
Gliese 581g - 0.45
Gliese 581d - 0.43
Gliese 581c - 0.41
Jupiter - 0.37
Saturn - 0.37
Venus - 0.37
Enceladus - 0.35
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Story Here
 
What are the limits that a human can live in that scale? Like .95 to 1.00 or something? Did I miss that in the article or is it not stated?
 
For some reason I was kind of hoping this would be fictional worlds and include things like quality of life, stability of government, environment.

Not sure if I want to retire on Bespin or Eternia
 
Perspicacity said:
For some reason I was kind of hoping this would be fictional worlds and include things like quality of life, stability of government, environment.

Not sure if I want to retire on Bespin or Eternia
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Wouldn't you be stuck on Cloud city on Bespin?
 
Mammoth Jones said:
I wish humanity would stop killing each other and just develop the technology to fly out there and go take a look ourselves.
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It breaks my hearth to see us wasting so much money in worthless endeavours that only serve a few privileged assholes when we could be bettering our world and exploring the cosmos. The current state of space exploration is a tragedy. Scientists would be weeping in the 60/70's if they knew what was ahead.

Sigh.
 
R2D4 said:
What are the limits that a human can live in that scale? Like .95 to 1.00 or something? Did I miss that in the article or is it not stated?
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I don't think we have the technology to know about that specifically because the first thing that would depend on is whether or not it has an oxygenated atmosphere so they looked at the things they COULD get at least some data on.
 
.89 is a high number, send something up there
 
Funky Papa said:
It breaks my hearth to see us wasting so much money in worthless endeavours that only serve a few privileged assholes when we could be bettering our world and exploring the cosmos. The current state of space exploration is a tragedy. Scientists would be weeping in the 60/70's if they knew what was ahead.

Sigh.
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Yea. I completely agree. Just like people like to scoff and say "Oh, it's impossible to go that far" I always think of some people trying to create the first boat and other people on the beach saying "That'll never work....you can't travel past all that water! It'll never float!"

Or people that said we could never reach the moon.

All it's going to take is one global catastrophe to wipe humanity out. Why? Because all our eggs (humans) are in one basket (earth).
 
Riposte said:
"War" tends to be the ultimate motivator in science. We just need to find ways to use Space to help kill each other.
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We did. It was called the Space Race. You don't think we did all that out of sheer scientific curiosity do you? That was the military industrial complex experimenting in plain sight.
 
Funky Papa said:
It breaks my hearth to see us wasting so much money in worthless endeavours that only serve a few privileged assholes when we could be bettering our world and exploring the cosmos. The current state of space exploration is a tragedy. Scientists would be weeping in the 60/70's if they knew what was ahead.

Sigh.
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I hope it will just be looked as the dark ages for space travel and once we get through them space becomes our bitch.
 
Napoleonthechimp said:
I never understood why Vulcan was such a big deal. It is so arid and barren... I thought the Vulcans where super advanced and intelligent.
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I never understood why Earth was such a big deal. It is so wet and teeming with bacteria... I thought the Humans were super advanced and intelligent.
 
Tom Penny said:
People believe in aliens? Crazy talk.
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QQEL5.jpg
 
fadetoblack said:
According to Wikipedia, the planet had been observed for ten years, but only announced in 2010. Early days, I s'pose, in space terms to send shit out there.
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The planet was announced last year? So, technically there could be planets with an even higher rating currently in development but science haven't announced them yet.

I hope the next planet is a new IP
(Intergalactic Planet)
and not just another Earth rehash.
 
DR3AM said:
.89 is a high number, send something up there
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With the current state of space travel, we're better off pooling our resources into improving our spacecraft.

We need to hit speeds at a respectable fraction of the speed of light before we go planet exploring :/
 
I watched some documentary the other day on national geographic.
They basicly got it down to warming up mars so it could become a livable place for us earthlings and earthveggies. And since we know how to warm up planets pretty well, we just need to apply that knowlegde there (just speed up the process some).
 
How does Jupiter even have .37. Does any chance of livability disappear at like .8 or something?
 
Spiffy_1st said:
The planet was announced last year? So, technically there could be planets with an even higher rating currently in development but science haven't announced them yet.

I hope the next planet is a new IP
(Intergalactic Planet)
and not just another Earth rehash.
Click to expand...

Yep. Mind blowing stuff, really.

Wikipedia said:
Gliese 581 g (pronounced /ˈɡliːzə/), also Gl 581 g or GJ 581 g, is an unconfirmed extrasolar planet, orbiting the red dwarf star Gliese 581, 20.5 light-years from Earth in the constellation of Libra. It is the sixth planet discovered in the Gliese 581 planetary system and the fourth in order of increasing distance from the star. The discovery was announced by the Lick-Carnegie Exoplanet Survey in late September 2010, after a decade of observation.
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OuterWorldVoice said:
How habitable her Uranus?
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Fixed.

Seriously though, they should keep this to solar-system celestial bodies, there are so many exoplanets already discovered with similar environments to that of earth, and many more assumed out there.

Titan is interesting though, where is Europa on the list, though?

Speaking of which, which mission would have greater support, one to drill and explore the underground oceans of Europa, or to submarines and ships to explore the lakes of Titan?

OR kill two birds with one stone and launch something that could drop a rover/exploratory robot on Europa while slingshotting to Titan and dropping it's sea/land rovers.




OR



 
How are even Jupiter and Saturn considered remotely habitable? Massively pressurized balls of supercritical fluids and plasma could sustain the development of the very complex molecules required for life? Yeah... okay...
 
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