2007-08-13 14:45:20 · 9 answers · asked by cemuni2 1 in Science & Mathematics ➔ Astronomy & Space
well, based on the idea of life needing water,
then at least 3 planets have been noted as probably having water
HD209458b
http://www.space.com/scienceastronomy/070410_water_exoplanet.html
HD189733b
http://news.bbc.co.uk/2/hi/science/nature/6292076.stm
Gliese 581 C
http://www.space.com/scienceastronomy/070424_hab_exoplanet.html
I'm sure there are more, but I can't google it all day.
2007-08-13 14:49:36 · answer #1 · answered by Mercury 2010 7 · 0⤊ 0⤋
An earth like atmosphere isn´t the issue. Just an atmosphere and the right temperature. Earths atmosphere was very much like that of Venus once. It was life that transformed the atmosphere into what we have today. It wasn´t the atmosphere that made life. So any kind of atmosphere would do but we could assume that an atmosphere that contains the substances life needed to evolve here should be the thing to look for. CO2, water and nitrogen combined at the very least along with temperatures that could allow water to flow on the surface. Life got along for almost 2 billion years without much oxygen in the atmosphere but if we do find oxygen in the atmosphere of an alien world then that would be a definite sign of life. But it wouldn´t be absolutely necessary for free oxygen to exist in order for the atmosphere to be able to sustain life. As far as I know no such candidates have been found besides earth. Only alien worlds that are at the right distance from its star to be in the habitable zone.
2007-08-13 15:08:01 · answer #2 · answered by DrAnders_pHd 6 · 0⤊ 0⤋
There are a few which have attracted attention lately. Two in particular are in the Gliese 581 system - planets C and D. C would be about half again the size of the Earth. It's a terrestrial (rocky) planet in the habitable zone, and would have a temperature range of about 0 to 40 degrees celsius. There hasn't been an atmospheric study yet.
D is on the other, cooler side of the terrestrial zone, but appears to be warmer due to the greenhouse effect. This one is less known, but it's more likely to support life - C is close enough to the sun that it could have a runaway greenhouse effect like Venus, turning it into a hothouse.
So those two are likely, but right now we don't have the resources to examine the make-up of their atmospheres. They are astronomically close, though - a mere twenty light-years away!
2007-08-13 15:01:48 · answer #3 · answered by ryttu3k 3 · 1⤊ 0⤋
Scientists can get spectrographic data for many of the over 200 exoplanets, and they have detected elements such as sodium, hydrogen, and other gas compounds around some of those planets.
Water is predicted to be among the most abundant (if not the most abundant) molecular species after hydrogen in the atmospheres of close-in extrasolar giant planets.
Several attempts have been made to detect water on such planets, but have either failed to find compelling evidence for it or led to claims that should be taken with caution.
However, many scientists believe that there is water vapour in the atmosphere of HD 189733b (a Jupiter-sized planet in close orbit around its star and therefore very hot).
The main problem is determining exactly what is needed to sustain life. Life-as-we-know-it has its own requirements but there is no proof that life that we know on Earth is the only type there is.
2007-08-13 16:03:33 · answer #4 · answered by Anonymous · 0⤊ 0⤋
How many outside the Solar System?
None.
How many inside the Solar System?
1 - the Earth.
One major thing you have to remember is that life itself created our atmosphere. The first plants created the oxygen. Animals did not exist until plants had been around long enough to produce enough oxygen for animals to exist.
Without plants, Earth's atmospheric oxygen would disappear, combining with the Earth to make oxides.
Nobody really knows what Earth's primitive pre-life atmosphere was like, so we would not know what to look for.
Nobody will find a planet with our atmosphere, unless it already has abundant life.
2007-08-13 15:32:27 · answer #5 · answered by nick s 6 · 0⤊ 0⤋
Drake's theory supposes that there are a total of 40 in the Universe, but more in-depth studies have reported a possibility of just a couple. Keep in mind that when we say "life" we mean any living organism.
2007-08-13 14:55:06 · answer #6 · answered by Sandy 2 · 0⤊ 0⤋
So far, zero. Some have been shown to contain and atmosphere and water (in some form), but none has been convincingly shown to have life-supporting atmospheres.
2007-08-14 07:05:07 · answer #7 · answered by Ryan H 6 · 0⤊ 0⤋
Not known currently. Suspicions/hopes about some, but not known.
2007-08-13 14:50:53 · answer #8 · answered by ? 6 · 0⤊ 0⤋
2. 1 is earth, the otha shld b mars.. but its too dusty..
2007-08-13 14:54:53 · answer #9 · answered by Anonymous · 0⤊ 1⤋