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64 votes
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Serious alternate form of the Drake Equation, or graffiti?

Given the font, it's xkcd 384, The Drake Equation. The two $X$'s are the other $f$ terms from the original Drake equation, while the $B_S$ is "amount of bullshit you're willing to buy from Frank ...
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  • 1,271
26 votes
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How many planets have we discovered that can support human life?

There is currently only one planet known to be capable of supporting human life, and you're on it. Several planets have been found in the region in which we expect water to be liquid on much of the ...
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  • 90.5k
20 votes

Could rogue planets harbor life?

There's also the possibility that a rogue giant planet may have a moon with a subsurface ocean of liquid water due to tidal heating in an orbit close enough to its parent planet. E.g. if Jupiter was a ...
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  • 1,538
16 votes

What is the probability of life having developed or going to develop in our solar system another time?

The answer is, it could be non-zero (some would argue it must be non-zero), but since we don't know what the probability of life emerging on Earth was, it is impossible to quantify. This is why this ...
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  • 117k
15 votes

Whats the probability of a hazardous impact for human life on Mars?

We actually have a very good idea of this because the Mars Reconnaissance Orbiter has been orbiting Mars for over a decade. The MRO is, basically, a spy satellite around Mars and is continually taking ...
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  • 7,390
13 votes
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Life planets orbiting black-holes. Can/Do they really exist?

Well, first things first. It's not likely to have a planet orbiting near a black hole and in significant time dilation because the tidal effects would likely tear anything that close apart. ...
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  • 22.9k
13 votes

Could rogue planets harbor life?

In short, if a rogue planet has enough internal heat and retains enough of that internal heat by a thick atmosphere or within a miles-deep ice crust, it could be warm enough for liquid water and thus ...
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11 votes

how far away could we detect that Earth has life?

I had put off answering this question because it seems too broad without specifying what sort of detection methods are proposed. But if you answer it directly from the perspective of - if we were to ...
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  • 117k
11 votes

How many planets have we discovered that can support human life?

You may be interested in the number of habitable zone planets. These are planetary-mass objects in a sort of "Goldilocks" region from their respective stars: This region is just right, given adequate ...
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  • 211
11 votes

What if we are looking for the wrong signs of life on other planets?

What if we are looking for the wrong signs of life on other planets? Are there any fields of astronomy that look beyond the "near-Earth" life comparisons and look for life in other (...
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  • 22.9k
10 votes
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What earth organisms might survive if they arrived on Mars?

On the surface of Mars probably none, since it's too dry or too cold, or both, to stay active. Spores or other dormant forms probably could survive for centuries, until radiation will gradually ...
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  • 11.2k
10 votes
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Is extra-planetary phosphine actually a new discovery?

You're correct; extraterrestrial phosphine is not actually a new discovery. As you said, we've known for decades (see e.g. Ridgway et al. 1976) that phosphine can and does exist in some gas giant ...
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9 votes
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Is the Drake Equation an accurate way of finding the probability of life on planets?

The Drake equation is little more than a randomly assembled guess of relevant factors for intelligent life, and any use of it requires a number of hard to justify guesses for the various probabilities....
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9 votes
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If we found evidence of life on Mars, how would we know that it originated on Mars rather than Earth?

Why would we assume that the early martian life originated on Mars, rather than Earth? There's still a whole lot we don't know. As Wayfaring stranger points out in the comments, Origin is a whole ...
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  • 22.9k
9 votes
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What is the underwater temperature of Europa?

No, nothing on Europa could possibly be photosynthesizing as we know it. Jupiter doesn't emit light, and what it reflects from the sun is not enough, plus there's no significant amount of carbon ...
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8 votes

Evolution of Life

Lets say you put a billion balloons on a dart board. Now lets say you throw a million darts at that dart board. If you were to pick a specific balloon and calculate the odds that THIS particular ...
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  • 1,952
8 votes

Could any known, living organisms on Earth survive on Mars?

I've read lichens have been shown to survive in a Mars-like atmosphere, tested by NASA. This other article says they can survive vacuum and radiation http://www.astrobio.net/extreme-life/lichen-on-...
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  • 949
8 votes

Proxima as Supernova

Proxima Centauri can't explode as supernova as it is about 2 orders of magnitude too small and light. But if a supernova were to happen from that distance? How bright would it be? You can use the ...
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  • 3,938
7 votes

Life planets orbiting black-holes. Can/Do they really exist?

Interstellar's "Miller's Planet" is utter rubbish... First of all, black holes don't start out as black holes. Black holes form at the end of the life cycle of very big star (at least 25 solar masses ...
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7 votes
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Why do scientists think life requires water?

When you lose your keys on a dark night you look where the probability of finding them is highest (which is a combination of being likely to see them with their probability of being there), which is ...
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7 votes

Why there are other planets in our solar system?

Did you mean to ask Would life on Earth be possible if Earth was the only planet in the Solar system? The answer is perhaps , we can only speculate and know too little about the evolution of the ...
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  • 5,276
7 votes
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The Solar System formation

I'll touch on a few of these because I disagree with some of those ideas. There are approx. 2000 planetary systems discovered, and all of them, except the Solar System, have angular momentum ...
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  • 22.9k
6 votes
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how far away could we detect that Earth has life?

Depends on what you mean by detecting life. As is explained in this what-if post by Randall Munroe, the algae on earth will tell the aliens about us before we can tell them about us. If you consider ...
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6 votes
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Plant on large Asteroid?

It might depend on what qualifies as a plant. A thin film of rugged mold for example . . . just maybe. The tricky part is that asteroids are too small to retain an atmosphere and you need an ...
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  • 22.9k
6 votes

Consequences of strong wind on an alien Planet on the possibility of life

We know that life can start and evolve quite well on a planet with 250 mph winds: You're living on one. The jet stream can reach this speed in the Earth's atmosphere. Beyond that it is speculation. ...
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  • 90.5k
6 votes

Most powerful microscope on Mars?

Having checked the older rovers, the highest resolution microscope on Mars is in the SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instrument. ...
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  • 90.5k
5 votes
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Do all stars have the potential to have life supporting planets?

Great question. The goldilocks zone is usually defined in terms of a region where the equilibrium temperature of the planet lies between some temperature limits (these temperature limits are somewhat ...
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  • 117k
5 votes

Evolution of Life

A "one time only freak accident" is only going to be considered as a likely possibility when scientists gain a deep understanding how life actually arises and on the basis of that can rule out that ...
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5 votes
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What planets and moons have we seeded with life (if any)?

This would seem to be constrained to planets and moons earth has landed on or impacted at all, as we have no way of telling after the fact whether a lander was perfectly sterilized. That list is as ...
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