PostHeaderIcon Answering Questions: Life on Other Planets?

Here are my questions:

1. What is the possibility that intelligent life on other planets exists?

2. Have we found any signs of life on other planets?

3. What is the possibility that any life will be found on a moon such as Europa or Titan?

Again, I greatly appreciate your time, and thank you in advance for your response.

Many Thanks,


Jacob, ahh, these are the questions driving our exploration of the solar system.

1. What is the possibility that intelligent life on other planets exists?

This question is more of an opinion question at this point than a science question. There are just beginning to be scientists attempting to put a number to the possibility that there is life on other planets. I’d like to break this question down.

Life within our solar system (other than on Earth)

There is no evidence of intelligent life within our solar system. This does depend on your definition of intelligent, but one definition sometimes used by astronomers is that intelligent aliens would be able to form civilizations and use radio communication. We would have picked up those radio signals long ago had they been created within our solar system. It is entirely possible that there is life that is not creating radio signals – but we might have detected that life in other ways too:  noticing extra heat, carbon dioxide, oxygen, or methane in the atmospheres of other planets and moons within our solar system.

There is a scientist – Dr. Abel Méndez from Puerto Rico who is studying how likely it is that life could survive (the habitability of) on various planets and moons. He has actually ranked Enceladus, Saturn’s moon, as having more habitable area than Earth!!

Life outside our solar system

Since we have not yet found evidence of life outside our solar system, we have no way of knowing if it is there or not. If you like, you can use the Drake Equation to make your own guess, based on your own choices for the percentage of stars that you think might have planets, and the percentage of those that might be habitable.  If you talk to your math teacher about how to use this formula you can get your own best guess. If you’d rather though, scroll to the bottom of this page and choose the numbers you like best, and the webpage will calculate it for you.

2. Have we found any signs of life on other planets?

Hmm. Not really. Scientists are looking for what they call “markers” of life or “markers of biogenic activity” (both phrases mean the same thing). For instance – if you see dog poop in the park, although the poop isn’t alive you can be pretty certain that there was a dog at that exact location not too long ago. Most of the markers scientists are looking for aren’t nearly as certain as that.


A while ago scientists studying Mars found new methane in the atmosphere. Methane is often produced when life forms digest food – it comes out of your body when you burp or fart. Bacteria make methane too, as do dogs, cows, and other animals. Unfortunately, the rock cycle can also make methane – especially when iron rusts. Mars is covered in rust – that’s why it is red. This discovery of methane could be either from geology or from biology, it is not necessarily a “marker of life.”

Magnetotactic Bacteria

Last week I wouldn’t have mentioned this, but there is a new scientific paper out this week. In 1996 scientists found what they thought were markers of life in a meteorite from Mars. This meteorite (ALH 84001) was discovered in Antarctica in the early 80s. There were two interesting things inside this meteorite: forms that might be fossilized bacteria, and strings of magnetite (a magnetic mineral). We can’t really tell about the shapes that might be fossilized bacteria, but the strings of magnetite are identical to magnetite strings created by certain bacteria (magnetotactic bacteria) here on Earth. This is a very new paper, so other scientists might have other ways to interpret the same information.

3. What is the possiblity that any life will be found on a moon such as Europa or Titan?

If you look at the work done by Dr. Abel Méndez it looks fairly likely that life might have begun on Europa or Enceladus. Titan is less likely, as is Mars. How likely is it that the life is still there or that we’ll find it? I don’t know. Scientists are constantly debating this one.

Useful Links

Dr. Abel Méndez on Planet Habitability

Methane on Mars

Magnetotactic Bacteria

Magnetotactic Bacteria from NASA

Advanced Links (My source material)

(These are source material, but I do not recommend them unless you want to spend hours piecing through the jargon)

Press release about Méndez’s work, with diagram

Méndez’s current abstract

Méndez’s previous article

~ A l i c e !

2 Responses to “Answering Questions: Life on Other Planets?”

  • Mrs. Baird says:

    Thank you for this website and information. We are using your website to evaluate web sources in class. We appreciate your resources. The kids want me to tell you they are all aliens. I don’t think they are legitimate. ;)

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