First Organic Molecules Found on Alien World 146
Galactic_grub writes "The detection of planet HD 189733b is in some ways just another small victory for extra-solar planetary science. It is too hot for there to be anything 'alive'. Just the same, somewhere on the planet are trace amounts of the gas methane. The fact that the element was detected at all offers hope for understanding future discoveries of Earth-like worlds, says NewScientistSpace. Researchers from Caltech and University College London used the Hubble Space Telescope to peer at the planet and examined spectral signature of starlight filtered by the planet's atmosphere, to identify different chemicals. 'The authors suggest that some ill-understood chemical process might be responsible, either concentrating the methane in cooler parts of the atmosphere, or generating extra methane directly. Alternatively, the methane might simply mean that the planet happens to be very rich in carbon.'"
Unfortunately, not a smoking gun... (Score:5, Interesting)
Also, the planet is around 700 degrees Celsius...why are we so sure this completely precludes the possibility of life?
Misleading (Score:5, Interesting)
The surprising thing here isn't that the astronomers discovered methane on a planet. Heck, Uranus is full of the stuff and other gas giants have it as well.
It's not surprising to find methane on an extrasolar planet. What is different about this is, to QTFA:
"Initially, that is surprising," says Sara Seager of MIT in Cambridge, US, who was not involved in the study. Because HD 189733b orbits very close to its parent star - just 10% of Mercury's distance from the Sun, it is very hot, with atmospheric temperatures of about 700 Celsius. "When the temperature is this high, the dominant form of carbon should be carbon monoxide, not methane," says Seager.
Re:Unfortunately, not a smoking gun... (Score:3, Interesting)
And even when that happens, it's still an organic molecule.
"700 degrees Celsius...why are we so sure this completely precludes the possibility of life?"
That may depend on how we define "life". In the sense that life could vary widely from what we know and understand, maybe you're right. Of cousre, if it's not a bit closer to "life as we know it" than that, then we don't know what to look for anyway. Would such life depend on water? Well, not liquid water. It wouldn't be made up of combustable carbon chains, either.
So within the limits of "life based on processes we understand", "life we have a clue how to look for", "life we have a reason to believe is possible", etc., it is safe to assume it couldn't exist in those conditions.
Drake Equation (Score:3, Interesting)
R* = The number of stars born each year.
fp = the fraction of those stars which have a planetary system.
ne = the number of "earth-like" planets in a solar system.
fl = the fraction of these planets on which life arises.
fi = the fraction of these life forms that evolve into intelligent civilisations like ours.
fc = the fraction of these civilisations that choose to attempt to communicate across the Galaxy.
L = the average time they have been trying to communicate.
The range of life forms found on Earth in extreme conditions have pushed the "ne" category into much higher ranges. You could make an argument for a lot bodies within our own solar system that have conditions less extreme than those found on Earth where life exists. We have found life in volcanic vents. We have found them in extreme cold areas. All of which really pushes "ne" closer to 1.0. And, solar systems seem to be more the rule than the exception.
Whether this planet can support life as we know it is a different proposition than what it means overall. The Drake Equation is getting pretty close to 1.0 in a lot of categories.
Re:Unfortunately, not a smoking gun... (Score:2, Interesting)
FTA:
Re:Unfortunately, not a smoking gun... (Score:3, Interesting)
And that doesn't strike you as a reason "we" are looking for familiar signs? How would you interpret things as life if you don't know how it would work, what it would consume and what produce? We would need to be able to closely inspect the planet to tell if we found life. But if we find familiar conditions, where we know with a high probability that certain reactions won't happen "naturally" and that the signature of products can't be produced in their relation to each other by natural processes (at least with a high probability), we have a much higher chance to tell life from other effects. Even so we still couldn't be sure.
So I would say looking for conditions known to be able to support life is the only thing which can do, because it is unclear if we would understand forms of life working completely differently to be alive.
Re:Unfortunately, not a smoking gun... (Score:3, Interesting)
Re:Drake Equation (Score:4, Interesting)
Dude! That's funny.
R* = We have some guesses from a few years of observation, but nothing approaching mathematical certainty.
fp = We just recently learned how to find planets, and the number found is extremely low compared to the number of stars found. It would be silly to try to assert with any certainty what percentage of stars have planets.
ne = Other than Earth, none have been found. No indication that any other will be found has been found. Nearly everything found so far have been gas giants orbiting close to their suns.
fl = Other than Earth, none have been found. No indication that any other will be found has been found.
fi = Other than Earth, none have been found. No indication that any other will be found has been found.
fc = Other than Earth, none have been found. No indication that any other will be found has been found.
L = Other than Earth, none have been found. No indication that any other will be found has been found.
If anything, the Drake equation is still sitting imperceptibly close to 0.
two reasons, chemically speaking (Score:4, Interesting)
All this has to take place in essentially an isothermal environment. We can't change the temperature of a cell by several hundred degrees to get different reactions to go in different ways, or forward and back. We can't compartmentalize the cell and have different temperatures in different parts so that different reactions are favored.
To get a set of chemical reactions that can be delicately balanced so that very small changes -- e.g. the addition or withholding of an enzyme (catalyst) -- can tip the balance this way and that, nothing is as useful as the hydrogen bond, which is a somewhat like a chemical bond in that it involves sharing a small charged particle between atoms, but in this case the particle is a proton instead of an electron. Since the proton is much larger than the electron, the bond is far weaker, typically. Helpfully, it can easily be broken and made at temperatures where water is a liquid by very small changes in the conditions. Indeed, they're made and broken in liquid water all the time.
You might easily say that life is fundamentally based around the existence of the hydrogen bond, and its ability to be formed and broken easily at certain temperatures. There really isn't anything else like it in chemistry. You couldn't imagine ordinary chemical bonds playing this role at, say, a much higher temperature, because the problem is that all chemical bonds become flexible and easy to make and break at about the same temperature (5000-10000 K). You couldn't have some bonds flexible and some others sturdy. It would be like trying to pour and shape steel with iron tools close to the melting point of iron.
Fortunately for us, because of the peculiar stability of the oxygen nucleus, there is a great deal of oxygen in the universe. Since there is also, naturally, a very large amount of hydrogen, it turns out that water (H2O) is probably the most common heteronuclear neutral molecule in the universe. There's a huge amount of it out there. And water is an ideal basic substrate on which to be building your life based on hydrogen bonds, because of course water is one of the best hydrogen-bonding substances there is. Think of it as the "silicon" in life "microelectronics," the substance that you can dope with other molecules and get all kinds of useful behavior.
It might well be the case that there is some other model for life, one not based on ordinary chemistry -- for example you could have Robert L. Forward's life based on nuclear chemistry, living on neutron stars, with a natural time-scale a billion or more times faster than ours. But no one outside of fantasy has ever proposed a plausible model for it.
Re:Drake Equation (Score:2, Interesting)