'Hundreds of worlds'

[xes]

No, we'd know if there was another sun in the solar system. Its gravity would affect things.

you've got an answer for everything,you have

 

[golightly]

No, we'd know if there was another sun in the solar system. Its gravity would affect things.

There was the theory that comets were caused by objects in the Oort cloud (or is it the Kuiper belt) being disturbed by a partner star to the sun, labelled 'Nemesis', and being sent into the inner solar system.

 

[Phenotypic Dai]

Any undetected earth-sized planets will be well outside the orbit of pluto and will therefore be incredibly cold places. Not suitable for life at all.

I think perhaps we're underestimating the durability of life. It's very hardy, and a complete fucker to get rid of.

The 'Rare Earth' hypothesis, that spawned the goldilocks zone, is deeply flawed. It seems to be suggesting that the conditions are suited to life, not that life has adapted to suit the conditions, as it should be.

Take the Jovian moon of Europa, for instance. It's well outside any goldilocks zone in our own solar system, yet it's an exciting candidate for life. It's surface of ice is covered in many deep cracks that seem to hint that beneath this lies an ocean of liquid water that's being heated by geo-thermal activity in the moon's core.

Even here on Earth, entire independent ecosystems have built up around the so called "Black smoker" vents that exist on the sea bed.

Europa could be a very interesting place to go fishing.

 

[Crispy]

Well europa is heated by tidal forces from jupiter mashing the core up. Without jupiter, a body the size of europa should have solidified much more by now. Rocky planets in the outer solar system will have to be big enough to retain heat from the formation of the solar system to sustain life today.

But yes, you're right, the 'goldilocks zone' is not a prerequisite for life (although it probably helps a great deal to have lots of liquid water and sunshine knocking about)

 

[goldenecitrone]

Having seen under what harsh conditions life can survive on earth I'd say it's virtually a certainty that the universe is teeming with life in all its myriad forms.

 

[Phenotypic Dai]

Having seen under what harsh conditions life can survive on earth I'd say it's virtually a certainty that the universe is teeming with life in all its myriad forms.

You see, I'm convinced of that too, despite there being no evidence for it.


Yet I mock creationists.

 

[david dissadent]

There was the theory that comets were caused by objects in the Oort cloud (or is it the Kuiper belt) being disturbed by a partner star to the sun, labelled 'Nemesis', and being sent into the inner solar system.

http://en.wikipedia.org/wiki/Oort_cloud

The Oort cloud (pronounced /ɔrt/ ort, alternatively the Öpik-Oort Cloud (IPA: [ˈøpɪk]: that is, as [ˈepɪk] with a rounded [e])), is a postulated spherical cloud of comets situated about 50,000 AU[1] from the Sun. This is approximately 1000 times the distance from the Sun to Pluto or nearly a light year. The outer extent of the Oort cloud places the boundary of our Solar System at nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun.

Although no confirmed direct observations of the Oort cloud have been made, astronomers believe it to be the source of all long period and Halley-type comets entering the inner solar system (some short-period comets, based on their orbits, may come from the Kuiper belt).[1]

http://en.wikipedia.org/wiki/Oort_cloud#Star_perturbations_and_Nemesis_theory

It is thought that other stars are likely to possess Oort clouds of their own, and that the outer edges of two nearby stars' Oort clouds may sometimes overlap, causing perturbations in the comets' orbits and thereby increasing the number of comets that enter the inner solar system. The interactions of the Oort cloud with those of neighboring stars, and its deformation by the galactic tide are thought to be the main triggers which send the long-period comets into the inner Solar System.[1][15] This process also serves to scatter the objects out of the ecliptic plane, explaining the cloud's spherical distribution.[16][17]

The known star with the greatest possibility of perturbing the Oort cloud in the next 10 million years is Gliese 710.[17] However, physicist Richard A. Muller and others have postulated that the Sun has a heretofore undetected companion (brown dwarf or gaseous giant planet) in an elliptical orbit beyond the Oort cloud. This object, known as Nemesis, is theorized to pass through a portion of the Oort cloud approximately every 26 million years, bombarding the inner solar system with comets. Although the theory has many proponents, no direct proof of the existence of Nemesis has been found.[18] Furthermore, many argue that a companion star at such a great distance could not have a stable orbit, as it would probably be ejected by perturbations from other stars.

http://en.wikipedia.org/wiki/Kuiper_belt

The Kuiper belt (pronounced /ˈkaɪpɚ/, to rhyme with "viper"),[1] sometimes called the Edgeworth-Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune (at 30 AU)[2] to approximately 55 AU from the Sun.[3] It is similar to the asteroid belt, although it is far larger; 20 times as wide and 20–200 times as massive.[4][5] Like the asteroid belt, it consists mainly of small bodies (remnants from the Solar System's formation) and at least one dwarf planet – Pluto. But while the asteroid belt is composed primarily of rock and metal, the Kuiper belt objects are composed largely of frozen volatiles (dubbed "ices"), such as methane, ammonia and water.

Personaly I dont buy the Nemesis hypothisis, but a through survey of impact creaters on all of the solar system should be able to pick up a 26 million year blip in the regularity of really big impacts.

 

[Crispy]

Not sure how hot our crater-dating techniques are...

 

[david dissadent]

The 'Rare Earth' hypothesis, that spawned the goldilocks zone, is deeply flawed. It seems to be suggesting that the conditions are suited to life, not that life has adapted to suit the conditions, as it should be.

Rare earth hypothesis is far more than just the temperature.

http://en.wikipedia.org/wiki/Rare_Earth_hypothesis

The moon plays a big part in it as well. A magnetic field probibly helps alot as well, but it may not be too important.

 

[david dissadent]

Not sure how hot our crater-dating techniques are...

Its based on statistical averages of how many small meteorite impacts are in a big one. The more small meteorites impacts the older it is.

Apollo help produce some corroberation of this technique. But it is a bit hit and miss.

 

[Crispy]

it is a bit hit and miss.

Arf!

But how do we know that asteroid impact rate is constant? If there was variation in impact rate, that'd screw up the estimates, right?

 

[david dissadent]

Arf!

But how do we know that asteroid impact rate is constant? If there was variation in impact rate, that'd screw up the estimates, right?

Id guess we would calibarate against the moon which we have physical samples for. I think it is also how they date lava flows and things like that on other planets and moons.

Actualy it gives me a bit of a brain ache just thinking about how complex it could be. Probibly a tiny little discipline full of controvosies.

I remember reading once that the reason NASA would not send 2 geologists to the moon on the same mission is that five minutes after they landed they would be throwing rocks at each other over competing theories.

 

[poster342002]

Having seen under what harsh conditions life can survive on earth I'd say it's virtually a certainty that the universe is teeming with life in all its myriad forms.

Yes, I think so too. I also suspect that there may be life evolved and adapted to worlds utterly unlike our own (I:E; beings that have evolved to breathe chlorine-based atmospheres, for instance, instead of oxygen).

 

[nuffsaid]

Having seen under what harsh conditions life can survive on earth I'd say it's virtually a certainty that the universe is teeming with life in all its myriad forms.

Problem with this theory I always have though is that live evolved where it could first then 'adapted' and 'evolved' to live in the harsher areas as time progressed, species developed and eco-systems were conquered. They didn't evolve in the harsh areas first.

If Earth just had deserts, ice-caps, mountain ranges and no deep sea thermals it might have taken a LOT longer for life to evolve and conquer these areas.

 

[goldenecitrone]

If Earth just had deserts, ice-caps, mountain ranges and no deep sea thermals it might have taken a LOT longer for life to evolve and conquer these areas.

Agreed, but then, how long is a lot longer? There's been life on earth for over three and a half billion years. That's quite a long time.

 

[david dissadent]

Agreed, but then, how long is a lot longer? There's been life on earth for over three and a half billion years. That's quite a long time.

Probibly about 3.7 billoin years.

From wikipedia

Scientific consensus is that abiogenesis occurred sometime between 4.4 billion years ago, when water vapor first liquefied,[2] and 2.7 billion years ago, when the ratio of stable isotopes of carbon (12C and 13C ), iron and sulfur points to a biogenic origin of minerals and sediments[3][4]