A Moment Of Reckoning for Cassini

No_Weak_Heart writes "The NASA/ESA Cassini-Huygens probe has caught sight of Titan and is now returning images that 'rival anything scientists have seen before - and that includes images from the Hubble telescope.' See more detailed images at the mission homepage."

Comments

Too Early!!

[bhima]

OK, I admit that I too am excited by the prospects of Cassini (OK! I mean the pretty pictures that Cassini will send us).

But this is a fuzzy dot!Can't we just wait a few months untill it's there.

Re:Too Early!!

[meringuoid]

But this is a fuzzy dot!Can't we just wait a few months untill it's there.

Then it'll be a fuzzy disc. It's Titan, proud possessor of the solar system's second smoggiest shroud. You're not going to see any detail through that lot.

Re:Too Early!!

[Anonymous Coward]

In the visible spectrum, probably not, but there may be something to see in the near IR or near UV range. Also, the Huygens probe has a camera on it, so we may get images during the decent. Plus Cassini has the capability to radar map the surface.

Oil? Oil! OIL!

[rylin]

...which is believed to support oily lakes and seas...

Americans! Invade!

Too close to capture all of Saturn

[Azahar]

Now that Cassini is so close that it can't take a photo that includes all of Saturn I think it is a good time to start paying more attention to the photos coming back.

This is one probe that promises so much that I have decided to enjoy the anticipation and appreciate the photos as they return, slowly and beautifully.

Saturn is the dream planet after all, all those rings, all that mystery. I can't say that I would like to live in orbit around it though.

Re:Too close to capture all of Saturn

[Profane MuthaFucka]

It can take a photo of all of Saturn in super high resolution. One piece at a time, digitally stitched together. We'll get one of those, don't worry.

Suspense

[smari]

I remember when Cassini was launched - I considered it my birthday present from NASA at the time. Now, it's not long to go... suspense is rising.

Let's hope they find something that gives the general public a run for their money; We need another space race or something to get people out of bed in the mornings.

When was the last time you saw a teenager staring at the sky in awe?

Little Green Men in our neighborhood

[Just Some Guy]

I know this is pretty off-topic, but given that we've never had a good look at the surface of some of these moons, is there any reason that they couldn't be inhabited be sentient creatures at the social equivalent of medieval Europe? Put another way, if there were a somewhat advanced society on Titan 1000 years ago, but one that hadn't ventured into space yet, how would they have been able to know that there was life on Earth at that time? We weren't broadcasting radio signals at that time, and hadn't made any large-scale modifications to the planet that would be visible from space (ie giant agricultural regions, cities at night).

I'm not a LGM kook - I have no expectation at all that we'd find any sort of life there. Still, is there any particular reason why we seem to be so sure of that?

Re:Little Green Men in our neighborhood

[deglr6328]

Well, its surface temperature is 95 Kelvins for starters(almost 300F bleow zero or ~20C above the boiling point of liquid nitrogen) there can be no liquid water on the surface. Also I don't think it is believed to have the great geothermal energy like the moons of Jupiter do because of tidal effects, so no energy there either. Finally, the sunlight it recieves is ~100 times weaker than what we get here on earth, with the amount that can actually get through the atmosphere and down to the surface much less than even this tiny amount. Life needs energy, lots of it, and there is precious little on Titan.

Re:Little Green Men in our neighborhood

[frankie]

any particular reason why we seem to be so sure of that?

Spectrometry. We've looked at all of the local objects fairly carefully and haven't seen signs of chemicals related to organic life as we know it. For example, Earth's atmosphere is full of highly reactive oxygen (aka fire, rust, krebs cycle, etc) and should not be abundant unless something is constantly producing it.

If memory serves, the atmosphere of Titan is not so different from that of the Earth a few billion years ago, before life began. So if there's life there, either it's inconceivably unlike us or it hasn't gone much up the ladder.

Re:Little Green Men in our neighborhood

[tigersha]

Arthur C Clarke once wrote a nice little piece called "Apes or Angels" (Ok, the title may be wrong). Basically his point is that the universe is 10 billion years old, we have been here for 5 million years. That is a tiny drop in the lifetime of the universe. So if we hit alien species the chances that life on the planet would be exactly in the same range as our evolutionary scale is pretty remote because 1 million years back or forth yould not be much in the tiemscale that the universe operates in.

There is a much better chance that they would be either millions of years behind us (bacterial or so) or millions of years ahead. They would more probably or not be either Apes or Angels.

Btw, this is one argument to use to say why we have not found any aliens yet: No ways to find bacteria on a long range and perhaps if they are millions of years ahead they would be so strange to us that we would not now what to look for. All advanced technology looks like magic.

So the chances of finding a civilization close to here which is about 1000 year ahead or behind us is pretty much zilch purely from a statistical point of view.

Of course, the argument does not quite hold in the Solar System since all the bodies in it are about the same age per definition (they were formed at the same time). But then you could still be talking a million years give or take. No human-like organisms then.

Re:Little Green Men in our neighborhood

[another_henry]

Actually the opposite is true - the colder a planet is, the more atmosphere it can hold on to. This is because the thermal velocity, that is the average speed of the gas molecules, depends on the temperature and increases on hotter planets or moons. If it's above the escape velocity, bye-bye atmosphere. Incidentally this is why the Earth has no hydrogen or helium in its atmosphere, because those lighter gases need less heat to reach high thermal velocities, and they just go zipping off into space.

Some chemist correct me here, but I don't think there's any potential energy in just the hydrocarbons. You need oxygen to burn them in as well, which Titan doesn't have. I can't think of a way to extract energy from them alone.

Re:Little Green Men in our neighborhood

[dutky]

Just Some Guy wrote:

But it does have a thick atmosphere, which would seem to mean that it has at least enough energy to keep a large amount of matter in a gaseous state. Also, that hypothesized hydrocarbon sea should hold quite a bit of chemical energy, shouldn't it?

No, just the oposite. If you want to have a thick atmosphere on a planet, you want to have very little energy at the surface. The smaller the planet, the lower ambient surface temperature (hence energy at the surface) required to sustain an atmosphere. If the ambient surface temperature is too high the average velocity of a molecule in the atmostphere exceeds the planet's escape velocity and all the atmostpheric gasses boil off into space.

Titan is a very small planet (larger than Earth's moon but smaller than the planet Mars), so the gravitational pull of Titan is somewhere between 1/3 and 1/6 that of the earth. Similarly, the escape velocity from Titan is much lower than the escape velocity for Earth, somewhere between the escape velocities of the moon and mars.

The only reason that Titan has any atmosphere at all is because it is so far from the sun that it is very cold. Primordial gasses that long since boiled off from the Earth's atmostphere (or Mars') are still trapped by Titan's weak gravity.

The point the other posters were trying to make is that decades worth of spectrographic studies of Titan's atmosphere have shown the atmosphere to be chemically neutral. It is thought that the presence of life would result in a chemically active atmosphere (one that could support oxidation, which the life-forms would use as part of their metabolic processes, just as we extract oxygen from the air in order to metabolize sugars, producing carbon-dioxide). We are not saying that the atmosphere must contain oxygen, or that all life must be based on a carbon/oxygen metabolism, only that the atmosphere must present some way for life to extract energy, or the by-products of some kind of metabolism must be evident in the atmosphere.

Since Titan's atmosphere is chemically neutral (mostly methane) there is no latent energy that could power living organisms, hence no organisms (at least, none that are still alive: they would have suffocated or frozen). If you say "But what if they are able to breath methane?" then you need to account for what they would do with the methane. Either you need to burn it (for which you need oxygen) or you need to get the energy from somewhere else (sunlight, for example). There isn't any oxygen in Titan's atmosphere, so burning isn't an option, and Titan is too far from the sun for sunlight to be of much use. That exhausts most of the possibilities.

None of this should be taken as proof that there is no life on Titan, or that life on Titan is impossible: it's just not very likely, given what we expect life to be like. If there were life on Titan, it would have to be very different from what we generally expect: it would have to use very small amounts of energy, and it might have to extract that energy from some very novel sources. We are talking something that is, essentially, indistinguishable from pebbles, rocks and sand. Even then, this life-form would need to have little or no interaction with Titan's atmosphere, otherwise we would see some effect from it's respiration in the atmosphereic chemistry.

Cosmic reboot event?

[Kap'n Koflach]

Arthur C Clarke once wrote a nice little piece called "Apes or Angels" (Ok, the title may be wrong). Basically his point is that the universe is 10 billion years old, we have been here for 5 million years. That is a tiny drop in the lifetime of the universe. So if we hit alien species the chances that life on the planet would be exactly in the same range as our evolutionary scale is pretty remote because 1 million years back or forth yould not be much in the tiemscale that the universe operates in.
Although the general point is valid, it is only really true if the conditions that allow intelligent life have remained the same for the entire history of the Universe. E.g. older stars were formed when there were fewer of the heavy elements (carbon, silicon, take your pick) required to support life, so they probably aren't harbouring ancient transcendant civilisations.

To take another example from Science Fiction ('Space' by Stephen Baxter), what if something happens every few billion years that wipes out all life across an entire region of a galaxy - such as a very energetic Supernova or gamma ray burst. This might simultaneously destroy life in many nearby star-systems, starting them again from scratch. Although finding a local civ that is exactly the same age/level as your own would still be very unlikely, this sort of reboot would level the playing field a bit.