Extraterrestrial Life

[Mats]

@Computergeek01 - No, my point was, how much money has been spent getting into space, or more specifically, to other objects in the solar system vs how much has been spent trying to go to the ocean-floor. My guess would be 100x more money was spent trying to get to space and that is why I ask the question, what is really more difficult?

[Computergeek01]

@ Mats: I'll admit that there is more interest in space exploration, but that isn't a measure of difficulty. I also know that the equations related to rocketry are posted online by both NASA and Estes Rockets and no, they aren't that hard to understand.

[Mats]

@Computergeek01: There's a difference between simple rocketry and actually landing a spacecraft on say, Venus. The required equations become a hell of a lot harder to understand. Complex trajectories need to be calculated for the spacecraft, taking into account planetary movement, solar wind and gravity. You have to calculate the landing onto the other planet very well, so as to not crash and burn once you get there. You also need to make sure you don't crash and burn here on Earth.

Also, parts that go into space must be shielded both against the G-forces experienced during launch and also solar radiation, including all the electronics. They must also be able to survive vast ranges in temperature.

The great number of failures in space missions, in spite of the billions of dollars/euros that NASA and ESA are allocated each year should suggest to you this is still not a simple task.

[Computergeek01]

@ Mats: Keep in mind we're talking relative terms here. Landing on another planet for example is not simple a simple task, I'm only saying that it is MORE simple then going to the bottom of the ocean. Let's break this problem down in to discrete tasks and solve them individually.

Complex trajectories need to be calculated for the spacecraft, ...

Why does it have to be a complex trajectory? Do you always have to navigate around something? To someplace like Venus or Mars it should pretty much be a straight shot.

... taking into account planetary movement, solar wind and gravity.

This is a three body diagram with external forces, you did this kind of math in high school.

You have to calculate the landing onto the other planet very well, so as to not crash and burn once you get there.

No you don't. What you need is an accelerometer in a negative feedback loop with the landing thrusters. Or a parachute, if we're talking about Venus the atmosphere is probably dense enough to use a parachute but if we're trying for someplace like Mars then it wouldn't work, that's a design consideration.

Also, parts that go into space must be shielded both against the G-forces experienced during launch ...

You accomplish this by "anchoring" cables down with a zip tie. You basically leave an inch or so on either side of the connection and use that slack to strap it to something sturdy like a metal frame. We do this with the network cables where I work so that in the event someone somehow trips over them the force of them pulling on the cable pulls on the server rack which is bolted into the floor instead of the socket the cable is connected to. I'm pretty sure there's an ISO standard relating to this.

... and also solar radiation, including all the electronics.

This is called a Faraday Cage, it was invented in the 1800's and you have one on the front of your microwave.

They must also be able to survive vast ranges in temperature.

This isn't as much of a problem as you're making it out to be. Most solid state electronics like cold temperatures. You wouldn't use a material that gets brittle in the cold but that's another design consideration. Thermal runaway would be an issue, especially when you are in space where there is no atmosphere to dump heat into. But that is the most difficult issue you've brought up so far and we know it to be a solved problem since satellites today run on RTG's. EDIT: The cold only gets to be a problem with batteries which need to stay warm enough to sustain their chemical reactions, sensors or optics might also be a problem but it seems that you should be able to find a balance between this problem and the one of thermal runaway I mentioned earlier, you can't very well have both of these problems at the same time on the same vehicle.

[Mats]

Why does it have to be a complex trajectory? Do you always have to navigate around something? To someplace like Venus or Mars it should pretty much be a straight shot.

The shot would be straight, but don't forget, the sun and planets warp space-time and even though the effect is slight, over such a large distance, you are going to miss by a long way if you don't factor that in.

This is a three body diagram with external forces, you did this kind of math in high school.

Actually, I did this kind of math last summer. Related to what I wrote above, it's extremely hard to calculate. Granted nowadays, it's done on computers using programs written for the purpose, however, mistakes are sometimes still made at this stage, so it can't be trivial.

What you need is an accelerometer in a negative feedback loop with the landing thrusters.

I agree with this part, but you still need to calculate an approximation of that landing to get an idea of how much fuel/how big a parachute. And let's not forget, one Mars mission was already lost by a failure to land correctly.

This is called a Faraday Cage.

I don't think they use a Faraday cage on spacecraft as the craft is being hit by all kinds of electromagnetic mess and that's not what a Faraday cage stops. In fact, I'm not really sure how they do protect their electronics.

This isn't as much of a problem as you're making it out to be. Most solid state electronics like cold temperatures.

Perhaps, but I suspect when you're heading inwards towards Venus it's not cold temperatures that you need to worry about.

The few things I didn't quote here I agree with. :p

[Ispil]

Well, I think this warrants a bit of perspective. Say you are holding a basketball, and your friend a tennis ball. Say that those are being used as scale models of Earth and the Moon, respectively. How far would you have to stand away from each other for the distance to be scaled? In school, it is likely shown to be just a little bit, likely not too far.

In reality, it's 30 feet or so. The scale of space is absolutely massive, far more than a list of massive numbers and units can represent. This web site shows this fantastically:
http://www.scalesolarsystem.66ghz.com/
As you can see, the distances are... well, ridiculous. The biggest issue with space travel as of now is that humans can't even survive in zero gravity long enough to get to Mars, let alone a round trip. At least, they won't survive in an Earth-like gravitational environment again. Of course, the obvious solution is to launch ships in the shape of a torus, as to create artificial gravity... but we can hardly launch objects large enough for that to be reasonable.

As for the original question, I don't think it is a question of whether there is a reason for there being planets with no life. The question is whether the results are able to be replicated, which we have yet to truly see. As long as we keep looking, we'll find it out there.

[htirwin]

The scale of space is absolutely massive, far more than a list of massive numbers and units can represent. This web site shows this fantastically:

That's one perspective. Another is that the distance is much smaller than the massive numbers with their units seam to us. Time is what is the true relevant measurement to consider. In terms of time, we are not too far away. For example we are about as close to Mars, with use of current technology, in terms of time, as someone in New York was from California 3 or 4 hundred years ago.

The issue of human health in space is an issue, but we don't really need people going along anyways. We are always talking about sending people here and there; I guess because it would be a "milestone", make us proud of ourselves, be a good story, an ultimate adventure, we can imagine it was ourselves in their shoes, , our president can give a good speech, have a moment of patriotic glory ... In reality, I could care less about whether a person goes there or not. Just take the pictures, do the experiments, test for signs of life, bring back the samples if possible, etc, and do it thoroughly. We've sent too many probes to other planets and moons and failed to just get these most important things right to start talking about sending people on grandiose round trip adventures. A better start would be to just bring back some samples. Unfortunately, plans to do this type of thing keep getting canceled.

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

[Stormboy]

@ hitrwin

And I don't think that probing for life is necessarily that difficult either. One of our first times on Mars, Viking missions ( late 70's) , we looked for microbial life, and we found something which they couldn't tell whether it was life or not.

That was exactly my point. As I have said we are probably missing something so we can't prove that it is a life form or not. There can be many types of positives like that but if we don't look into it in great detail and research on it, we can't prove it. They are researching "whether life is possible in this planet or not" by looking at its chemical, atmospheric and surface details rather than sending probes to that planet and explore the surface or dig deep down. Whenever they find that the planets conditions are somewhat similar to Earth, then they send robots to land, such as that on Titan (moon) as it looked very suitable. Results would be more accurate if a robot landed on a planet looked for the carbon dioxide/oxygen change in the atmosphere or something similar rather than calculating it by sitting here on Earth.

As far as I understand, since then we have not looked for life on Mars, even the recent exploration in 2012, they conducted no tests for biological life. I'm actually not sure if we have conducted tests for biological life off this planet since then at all. And the tests they did even during Viking was only a scratch on the surface.

Why do they even stop looking? No wonder we don't find any life. They focus on surface details and other stuff as I have said rather than life.

[Mats]

That which was found in the 70s was not actual life. It was possible evidence of a fossil of life. That fossil, if it was indeed a fossil, could have been from when Mars had liquid water. In fact, all life on Earth may originate from Mars. This is not a crackpot theory, but a decent theory based upon sound science. (see Panspermia).

As for looking for life on moons, although Titan is considered far too cold (about -180C) for life, there are moons which are reasonable candidates for life - Enceladus, Dione and everyone's favourite candidate - Europa.

[Ispil]

...we actually did continue looking for life on Mars, and determined that the only possible life actually there is incredibly small, due to the fact that there is essentially no methane in the atmosphere. So yes, we have been looking for life on Mars for quite a while after, and only found evidence of it not being there. There is water on Mars, however- just no methane.

[htirwin]

They looked for methane, but did not do tests for biologic life. Even if they found a ton of methane, it wouldn't prove there is life on Mars. At no point since Viking has there been a missions with the intention of finding life itself, i.e. tests for life. This means that there had never been any chance that any of those missions could have resulted in proof of life, even if it existed.

[htirwin]

That which was found in the 70s was not actual life. It was possible evidence of a fossil of life. That fossil, if it was indeed a fossil, could have been from when Mars had liquid water.

Not true.

Biological experiments
Main article: Viking biological experiments

The Viking landers conducted biological experiments designed to detect life in the Martian soil (if it existed) with experiments designed by three separate teams, under the direction of chief scientist Gerald Soffen of NASA. One experiment turned positive for the detection of metabolism (current life), but based on the results of the other two experiments that failed to reveal any organic molecules in the soil, most scientists became convinced that the positive results were likely caused by non-biological chemical reactions from highly oxidizing soil conditions.[11]
Dust dunes and a large boulder taken by the Viking 1 lander.
Trenches dug by the soil sampler of the Viking 1 lander.

Although there is consensus that the Viking lander results demonstrated a lack of biosignatures in soils at the two landing sites, the test results and their limitations are still under assessment. The validity of the positive 'Labeled Release' (LR) results hinged entirely on the absence of an oxidative agent in the Martian soil, but one was later discovered by the Phoenix lander in the form of perchlorate salts.[12][13] It has been proposed that organic compounds could have been present in the soil analyzed by both Viking 1 and 2, but remained unnoticed due to the presence of perchlorate, as detected by Phoenix in 2008.[14] Researchers found that perchlorate will destroy organics when heated and will produce chloromethane and dichloromethane, the identical chlorine compounds discovered by both Viking landers when they performed the same tests on Mars.

The question of microbial life on Mars remains unresolved. Nonetheless, on April 12, 2012, an international team of scientists reported studies, based on mathematical speculation through complexity analysis of the Labeled Release experiments of the 1976 Viking Mission, that may suggest the detection of "extant microbial life on Mars."[15][16]

http://en.wikipedia.org/wiki/Life_on_Mars#Viking_experiments

[Mats]

I was thinking of that martian meteor thing they found. I had no idea the Viking experiments had gone so far! =0 Very interesting stuff htirwin!