There is no intrinsic reason why life could not survive on an asteroid. One theory for the origin of life on earth posits that life originated in microscopic water-filled pores in rocks buried within the earth's crust. Here the environmental conditions would have been stable, protected from the ravaging effects of meteorite impact and deadly UV radiation amongst other hazards extant on the primitive earth some 4 billion years ago. Because temperature and pressure go up as one moves inside of an asteroid (or planet), conditions compatible for the existence of liquid water go up. In almost all theories, water is the necessary medium for life's developmemt.

As far as the search for life, we can only hypothesize from our limited experiences here on Earth. Very probably we are underestimating the potential forms life could take on.

These are very interesting questions and astrobiology is the field of inquiry that is most relevant to these questions. Some of us at UCSB are actively involved in this research: the origin of life and understanding the physical conditions on earth 4 and 1/2 billion years ago. This is a very fun job!!!!

I think it is theoretically possible that life could exist on an asteroid, but the chances of this happening would probably be small.On the other hand, one theory on how life got started on Earth is that the chemical building blocks of life came to Earth by way of meteorites, which could have been asteroids before they crashed to Earth.

I am curious as to what the six characteristics of life are that you refer to. Could you e-mail me back and tell me? Some recent advances by mathematicians, biologists, and philosophers this century has come up with a definition of life that has three characteristics: living things are self-bounded (they have physical limits to their bodies); they are self-generating (they can spring from nothing or a seed or a single cell); and they are self-perpetuating (they keep themselves going by their own devices, mostly by regulating the flow of energy). I got these from a book called The Web of Life, by Fritjov Capra.

>
> In response to your question here are our six characteristics of life:
> -Responds to stimulus
> -Death/Reproduction
> -Eating
> -Growth and Development
> -Respiration
> -Made of Cells
>
> Thank You!
>

Thanks for sending me the definition of life you use. This is not an easy topic, and philosophers and biologists and computer scientists all have something to say about it.
I have a couple of puzzles, then, to tickle your brains. Is a mule alive? (It cannot reproduce.) What about a virus? Do plants eat? Have fun thinking about these!

Scientists certainly think so. On earth, there are places that you would think that nothing could survive but it does. Typically this life occurs as bacteria or some other microscopic life form. This kind of life has been found in thermal vents on the ocean floor where the water temperature approaches boiling and there is so much sulfur and toxic gases that most life forms would die. There is no reason to think that life couldn't
survive other extreme environments.

>On Earth there are six characteristics of life. In the search for alien life forms are the characteristics of life the same?

Good question! Hard to answer. Suppose you are on NASA's astrobiology team and your job is to design probes that search for extraterrestrial life. You have to first define life before you can design a probe to search for it.
So, in these searches, probes generally are designed to search for what we define as the characteristics of "Earth" life but scientists also try to expand the possibilities as well. For example, it is not necessarily true that all life in the universe be primarily carbon-based (like it is on earth), so how would you design a probe that was not carbon-specific? It's very difficult to know what to look for, and requires lots of imagination.
Also, many scientists now look at Earth's own "extreme" environments (such as deep ocean vents and Antarctica ice) and the organisms that live there to modify the "characteristics of life" that might be used as probe parameters. Some people think that it might be more efficient to search for living "planets" rather than individual life on various planets or other bodies. Do you have ideas about what kind of probe you would build to search for that?

It is hard to imagine that earth-type life could survive on an asteroid. It just doesn't seem like the resources necessary to support life would be available. On the other hand, life has been found on earth in some places with very harsh environments.

The scientific definition of life is supposed to be very general and should apply to all forms of life. There is always the possibility of making a discovery that would change how we look at life.