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Exoplanet near Gliese 581 star 'could host life'
A red dwarf star 20 light-years away is again providing hints that it hosts the first definitively habitable planet outside our Solar System.
The planet Gliese 581d is at the colder outer edge of the "Goldilocks zone" in which liquid water can be sustained.
Now a study in Astrophysical Journal Letters suggests its atmosphere may keep things warm enough for water.
The solar system also hosts another contender for habitability, unconfirmed planet Gliese 581g announced in 2010.
However, the existence of that planet has since been called into question.
Gliese 581d is less controversial; it was discovered along with the planet Gliese 581c in 2007, occupying the outer and inner edges of the Goldilocks zone, respectively.
Gliese 581c was soon determined to be too close to its host star to sustain water, with a surface temperature exceeding 1,000C.
Conversely, the outlying planet 581d - with a mass about six times that of the Earth and twice its size - was initially taken to be too cold to have liquid water.
Now, French researchers have run computer simulations of the planet's atmosphere, arguing that it is likely to contain high concentrations of carbon dioxide.
They contend that conditions could be suitable for oceans of liquid water as well as clouds and rainfall.
However, Gliese 581d's denser air and dim red light from its host star would make for a murky environment that would be toxic to humans.
Robin Wordsworth, a member of the team from the Institut Pierre Simon Laplace in Paris, said that the findings were further evidence that the sheer variety of planets and environments far outpaced that which we see in our own Solar System.
Dr Wordsworth said that the simulations are tantamount to a first definitive claim for a habitable exoplanet.
"This discovery is important because it's the first time climate modellers have proved that the planet is potentially habitable, and all observers agree that the exoplanet exists," he told news agency PA.
"The Gliese system is particularly exciting to us as it's very close to Earth, relatively speaking. So with future generations of telescopes, we'll be able to search for life on Gliese 581d directly."
They shouldn't say "habitable planet." We just know that it passes the first two tests to be habitable: (1) it's got a solid surface, and it isn't just a ball of gas; (2) it's in the goldilocks zone. But we don't know what else it is. For all we know, it might be exposed to strong x-rays or particle streams that would kill any self-replicating molecule as soon as one appears. "Habitable" is too strong a promise.
"Potentially habitable" is exactly the right descriptor. Science journalism is almost always really bad.
Venus is actually on the inner edge of the goldilocks zone and is solid but its as far away from habitable as you can get.
I dispute that. I often think that Venus is overlooked as a source of life.
Life can live in some pretty harsh environments. At the bottom of the ocean (intense pressure) around volcanic vents (high temperatures and toxic gases).
If you've ever been to Yellowstone, and seen the blue or green pools of boiling water, the color is from bacteria living there.
And then there is the possibility of airborne life in Venus's atmosphere.
So don't write off Venus.
Venus is too harsh for organic molecules to exist. They would be broken down by the heat.
The temperatures vary widely at different levels of the atmosphere. And the atmosphere is packed with organic particles.
There are a fair amount of life forms living in our atmosphere, even at high altitudes.
I don't know how or where to upload a PowerPoint to share with those who may be interested, but I did a presentation on extremophiles and possible life on Mars in my Bio class at UAkron.
So I'll just copy-paste some bullet points from two slides that I think are interesting and a bit relevant to the thread.
And what rough beast, its hour come round at last, Slouches towards capital to be born?
I'm equally concerned by the sulphuric acid rain.
But they need a platform on which to "experiment."
There are many organisms that can survive acid baths (h.pylori, for example, decided to colonize my stomach once, little imperialist bastards).
The real problems is that without a rock or a pool or something like that for the chemicals to interact, life isn't going to arise. It's possible some hardy bacteria hitched a ride from another world, but unlikely.
True but the fact that most organisms would be pretty much disintegrated by acid (especially hot acid being boiled at temperatures approaching if not in excess of 400 degrees celsius) pretty much narrows the chances of that down even more. Add to the fact that due to Venus's thick coat of clouds any bacteria hitching a ride on a meteor would burn up in re entry. Nothing is surviving that, not even extremophiles.
Life needs generally needs water and/or oxygen to stand a chance, on Venus you arent going to find either.
The USSR sent a lander to Venus, they found fuck all except this
Incidentally this lander would have survived about an hour before it melted on the hot surface.
I was thinking more hitching a ride from, say, Mars, on rocks ejected from a comet or asteroid strike, and somehow detaching in the Venusian atmosphere, where the heat wouldn't destroy it. The circumstances would be astronomical, but it's within the realm of possibility, for microbial life to exist in the clouds of Venus, or elsewhere. Just not very probable.
So is it time to start building those self-replicating probes Michio Kaku keeps talking about?
We can do it guys!
Don't forget to knock!
The enemy is someone whose story you haven't heard yet - Mid-East dialogue
I'm talking thermal physics here not Venusian meteorology. Its impossible for any body to enter Venus without undergoing phenomenal heat simply due to the enormous pressure differential from going to an absolute vacuum to going to 2x10-12 kg/m3. The atmospheric density of Venus is far greater than Earth (over 90 times greater). Any spacecraft that reenters the Earths atmosphere can be observed being engulfed in a plume of flames due to the enormous friction during re entry (Think of jumping of a diving board and landing in deep water belly first, it is a similar principle) and depending on the size of the object, the temperature experienced could be several thousand degrees celcius. That goes up even more when you're dealing with atmospheres that are denser again than the Earth, as has Venus.
Actually, people who've piked up meteorites have reported them being extremely cold. The flaming trail isn't the meteor burning, but ionized gas in front of the object. Because of the heat, the surface of the meteor facing forward melts, and is ablated off by air, but the rest of the meteor remains just a few degrees above absolute zero.
I just finished reading Phil Plait's Bad Astronomy, where he writes about this, phenomenon.
Like I said, it is extraordinarily unlikely, but then again, so is our being here at all.
That depends on 3 factors- the original surface area of the meteorite (A smaller one will be more aerodynamic and possibly deflect less heat), time between impact to the person picking the meteor up, and the chemical composition of the meteorite. If the composite material of the meteorite undergoes an exothermic reaction with the earths environment that would cause it to cool down.
I'm curious, what possible sources of X-rays or "particle streams" could there be?
My issue RE the potential habitability of this planet is that carbon dioxide is readily available from abiotic sources. A more convincing sign of life would be the detectable presence of volatile chemicals such as oxygen and methane, which rapidly (in geological timescales) bond with other chemicals or break down if not constantly replenished by biological activity.
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That's not the cause. The cause is that they are exceedingly cold to begin with, only a few degrees above absolute zero. When we see a trail, it's not the meteor burning up, but ionized gases in front of the meteor glowing. Because of the heat of these gases, the forward part of the meteor begins to melt, and ablates off of it, which we see as a trail. Only this small part of the meteor actually heats up, and then by the time it gets to the thicker part of the atmosphere, it slows and reaches terminal velocity, and then just falls to Earth.
