• Question: How do we know if there are Aliens? And how would we find out?

    Asked by ejrw to Adam, Catherine, Karen, Leila, Nazim on 13 Mar 2012. This question was also asked by graciemay, decy, sophiej, buddingscientist.
    • Photo: Adam Stevens

      Adam Stevens answered on 10 Mar 2012:

      The easiest way to find aliens would be to meet them! However, to meet other organisms from another solar system would require them (or us) to have spaceships that are really technologically advanced, way more than we have now.

      The most likely aliens we will wind will be microorganisms, bacteria basically. These will be harder to find.

      If we do find a living bug it would be amazing, but that might still be difficult. Alien life might not look like what we’re used to, so we might miss it. Normally we would look for things like respiration or photosynthesis or some kind of metabolism that make products that we know about (like we breathe out carbon dioxide).

      It’s a lot more likely that we will find past life though, and that’s even harder. We would need to find /signs/ of life rather than life itself. Fossils of microorganisms would be good, which is think is Leila’s speciality, but bugs don’t always get fossilised. We could look for leftover remnants of their waste, or other evidence of life processes.

      At a very basic level we are looking for organic molecules (ones that are mostly made up of carbon). It turns out that organic molecules are abundant in the universe. We have found some even in the depths of space! These molecules are what living things usually build themselves out of.

      If alien life is totally different to life on Earth though, it could use different elements to build its DNA or not even use DNA at all. In that case it might be really, really hard to find!

    • Photo: Leila Battison

      Leila Battison answered on 10 Mar 2012:

      The big problem is, we don’t know if there are aliens or not!

      Based on the numbers of stars and planets in the galaxy, and a few other factors that are harder to work out, there could be as many as a million intelligent civilisations out there. But despite listening and looking for them with radio telescopes and messages, we have had no sign of aliens at all. The problem is, space is unbelievably huge, so it would take hundreds or thousands of years for messages to travel backwards and forwards between the stars. The chances of picking up a message in the 50 years or so since we started listening are quite small. So scientists are changing their approach, to look instead for closer, but more primitive types of life.

      Like Adam says, we can look for these primitive bacteria either living or dead on the surfaces of planets, moons and asteroids in our own solar system. I look at fossils of dead bacteria on Earth to try and work out how we can use cameras or chemistry to spot them on other planets. It is tricky, because they can look just like grains of sand if you don’t know what you’re looking for. You need to match their size, shape, and what they’re made of, to living bacteria, to make sure you’re really looking at a fossil.

      Organic molecules, like carbon, or the amino acids that make up proteins on earth, are good hints for life. We have found some of these in meteorites and in water spraying out of the bottom of Saturn’s moon Enceladus, but they are just one piece of the jigsaw, and more signs are needed to prove they came from life.

    • Photo: Catherine Rix

      Catherine Rix answered on 11 Mar 2012:

      Because the universe is so huge there could be aliens out there and we could never travel the huge distances to meet them. In the project I’m working on we are trying to look for evidence of life on Mars. Mars is a good place to start because its relativly close to the Earth and we can send spaceships there – it takes about 9 months to fly there. There aren’t little green men on Mars but we think that there might be microbes, or that microbes might have lived there in the past. If we can find life on Mars it makes is much more likely that there is life on other planets too.

    • Photo: Karen Masters

      Karen Masters answered on 13 Mar 2012:

      Space is really big so it’s really unlikely that they could ever make it here if they even existed. Our only real chance of finding aliens is detecting their signals, and there are projects working on that. In fact you can help – if you visit http://setilive.org/ run by my friends who set up Galaxy Zoo you can look at signals from the Allen Telescope Array and see if you can notice anything unusual which might have come from an alien.

    • Photo: Nazim Bharmal

      Nazim Bharmal answered on 18 Mar 2012:

      We might never know if there are aliens. We can listen for them, using radio or watching for bursts of light they send (perhaps as laser beams). We might detect them if they create pollution on the planet they live on.

      There might be a good chance we will never see any evidence for them, but we can never be sure.

      There is an equation predicting how many alien civilisations there are likely to be able to be detected in the Milky Way, the Drake equation, but a lot of the numbers in that equation have to be guessed.

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