Supporting data for other stuff I mentioned here and there in the above. Not that I made any extraordinary claims, as it's long been stuff that atmospheric scientists, planetary geologists and space biologists etc have been stating, and hence [color="#FF0000"]the following is about 1.5 decades old[/color]. (Reason behind choice of source is that, despite the early date/despite there being far more recent stuff, quoting from a single source is easier than having to dig out multiple. Also, I remember stuff from that era better)
Quote:Could life have arisen on Europa? It's hard to guess until more is known about how life began on Earth. How easily did life emerge? Was it a miracle never to be repeated?
To answer that, you have to travel back in time to the beginning of Earth's history.
Steve Mojzsis: "Life must have arisen after the formation of the planet, about 4.5 billion years ago. But how soon after, how quickly after? These are questions that we are trying to answer from studying the geological record of the oldest rocks."
Steve Mojzsis is a geologist turned fossil hunter. To probe the earliest secrets of the planet, he travelled to Greenland, where a rare outcrop of ancient rock survives almost unscathed from when the Earth was young. In those rocks, he hoped to find microscopic traces of the most ancient life forms imaginable. During a field trip in 1995, he gathered a haul of sedimentary rocks, minerals that had formed at the bottom of the world's first ocean.
S Mojzsis: "The rocks that are the oldest sediments of all have been through everything you can do to a rock without quite melting it. They've been thrust up, regurgitated, ground up, heated, crushed..."
When he broke open the rocks, he found in them tiny mineral grains.
He suspected they might be the charred remnants of primitive microbes.
S Mojzsis: "It's a preserved kind of a time capsule, this little mineral."
Mojzsis put some grains into a machine called an ion-probe, which deciphers the precise make-up and age of the minerals. If the small lumps were once living things, they'd have a specific chemical fingerprint.
"We found out it was spot on. A veritable stamp ... of ... life that's unique to it."
But the real surprise was the age: the ion-probe showed that the fossils were nearly 4 billion years old.
"As far back as we can go, 3.9 billion years ago, there IS evidence of life, that life DID exist here. And it existed soon after the Earth formed. And that became something of a surprise to us."
It had been thought that the Earth was uninhabitable for nearly a billion years. But now it seems that life sprouted almost as soon as the Earth itself came into being.
[color="#0000FF"]"As long as life appeared here so quickly, then perhaps it's a kind of cosmic imperative, that life *should* appear as a chemical consequence of the evolution of a planet."[/color]
Life took hold *here* [color="#800080"](on early Earth)[/color], not in the temperate cradle of today's Earth, but when the planet was a steaming cauldron.
If life began so easily, then perhaps the Earth isn't so special after all.
If life began when the Earth was to all intents an alien world, what happened billions of years ago on the other planets? [color="#800080"](<- While it's largely speaking of our solar system in the specific context, the principle applies to any other solar system's planets too, of course.)[/color]
[...]
We now know that pieces of Mars have been raining down on Earth for billions of years. Could life have once travelled with them?
[color="#0000FF"]Chris McKay, NASA AMES Research Centre: "If life was present on Earth at the end of the formation of the Earth, well at that period, the impacts would have been much more numerous than they are today. And so material would've been constantly been/being knocked off the planets - all of the planets - and exchanging between the planets. So they could have carried organisms from one planet to another. The planets would Not have been biologically isolated. This material going back and forth would have been sort of like swapping spit between the planets."[/color]
(B-TP-7)
Quote:As the Sun continues to heat up [color="#800080"](over 2 or 3 billions of years from now, when the Sun is on its way to the Red Giant state)[/color], this little moon [color="#800080"](Saturn's moon Titan)[/color] will also come into its own.
Greek (?) scientist, Dr Athena Coustenis, Observatoire de Paris**: "It's the only other planetary object that looks like our own Earth. It's the only other object we know of that has an atmosphere of Nitrogen. And also we know that there is an organic chemistry taking place inside this atmosphere, and we have the creation of all those molecules that we find on earth. The only thing that is lacking is a little bit of temperature, a little bit of heat and a little bit of oxygen."
[color="#800080"][** IIRC, she came up with a way to work out the elements that made up a distant planet's atmosphere. Still spectroscopy, but the traditional technique used for starlight couldn't be applied directly, since planets don't tend to burn gas/don't tend to give off light of their own (we don't tend to see distant planets of other systems) unlike the light we see from stars/suns.][/color]
In Paris, Athena Coustenis and Chris McKay [color="#800080"][were][/color] studying some of the [color="#800080"][then-][/color]latest telescope images of Titan.
Chris McKay: "Right now it's very cold [color="#800080"](on Titan)[/color]. But it has all the ingredients to being a very nice place to live. In some sense it's like a pie frozen in the freezer, and when the sun gets more bright, it will warm up and bake, and have a nice water-rich environment, with a nitrogen atmosphere. And we know today that there is rich organic chemistry occurring in the haze in Titan's atmosphere. That organic chemistry could in fact be the seeds for life, so even if life from earth doesn't migrate to Titan, Titan could initiate life of its own when the Sun becomes bright enough to cook that pie."
Dr David Black, Lunar and Planetary Institute: [color="#0000FF"]"One of the things we've learned in astronomy is that all young stars have discs associated with them. Now we believe these discs are the precursors, the things out of which planets are formed."
How many of these discs of dust actually go on to form planets is unknown.[/color]
[...] [color="#800080"]<Planet Hunting segment. Back then they were apparently averaging one new planet discovered in our galaxy per month. Found from deduction/inference based on astronomical data, using method well-described long ago in CS-C.>[/color]
Dr David Black is chairman of the NASA "Origins" programme, a programme designed to search for the signs of life in space.
[color="#800080"]<Origins telescope - space telescope of NASA Origins programme - can show tiny images of planets, as dots>[/color]
But what can a dot of light tell us about another planet far away in the universe? Before the probe Galileo headed for Jupiter, it looked down on Earth to see if life could be detected from space.
[...]
Dr David Black, Lunar and Planetary Institute: "What Galileo [color="#800080"](NASA mission to Jupiter)[/color] showed us was that, in fact, these molecular signatures - that we think are indicative of life on the planet - were really there and you could separate them out, so it gave us some confidence that by looking for similar signatures when we look at the atmospheres of other planets, that we could maybe infer from those signatures that life was there as well."
The signs of life as we know it are universal. The combinations of chemicals on Earth could be repeated on any planet in space. And all of these chemicals are now identifiable from a distance.
[color="#0000FF"]Dr David Black: "And we'll be looking for things like signs of water in the atmosphere; carbon dioxide - which would indicate that it's got a substantial atmosphere; ozone, which says that there is oxygen in the atmosphere. And all these taken together, each one tells you something about the likelihood that the planet is either inhabited or maybe habitable.
If you can find methane, especially with oxygen in the atmosphere, it's a slamdunk - as we say in America in basketball - that you can conclude that life is on that planet."[/color]
And in the right place in a solar system, many now believe that the combination of these elements will almost certainly mean life.
Professor Geoff Marcy, San Francisco State University: "If you hand a biochemist [color="#0000FF"]a planet with a rocky surface[/color], with a temperature that's not too cold so that the water is frozen into ice, and not so hot that the water is evaporated into steam, but [color="#0000FF"]a temperature that[/color] - in the words of Goldilocks - [color="#0000FF"]is 'just right' for the liquid form of water, it will pool into lakes and rivers and streams and of course oceans. And the biochemists are unanimous that the laws of chemistry will take over. You'll end up with complicated organic molecules that we in fact would call life."[/color]
But we've yet to find a planet that falls within this Goldilocks zone, and is rocky and small enough to be suitable for life - like the Earth.
[color="#800080"]<IIRC, it here goes off into potential considerations like Jupiter's moon Europa? Forgot to check.>[/color]
(B-TP-8)