Expert: Ed - 9/8/2006

Question
That's brilliant, Ed! In terms of lifespan I thought it might be measured in years. Would you be able to give me an answer in years by any chance? Also what about Phobos? Will that crash in about 50,000,000 years? Is that short in terms of lifespan of a moon in an astronomic context?

Many thanks for your prompt reply.


Michael
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Followup To

Question -
Good afternoon.

Please would you tell me the shortest life span of a confirmed moon?

Many thanks,


Michael

Answer -
Michael,
I'm not sure exactly what you mean.  Please give me more detail.  

I can tell you that Jupiter's moon Io is considered to have the youngest surface features, because Io is so incredibly volcanic that everything we can see there has come out of volcanos in the fairly recent past.  I suppose that you could therefore say that Io has had the shortest lifespan of known moons.  Does this answer your question???

http://solarsystem.nasa.gov/planets/profile.cfm?Object=Io
http://en.wikipedia.org/wiki/Io_(moon)#Physical_characteristics

I hope this is helpful to you.  Please let me know if I've totally misunderstood your question.

Keep Looking Up!!!
--Ed

Answer
Michael,

Well, at least part of Io's observable surface is only five years old.  That's FIVE, with no zeros after it.  As you probably know, in astronomy you can usually expect at least six or seven zeros at the end of any number that you come across.  But, in 2001, the largest volcanic eruptions ever seen anywhere in the universe occurred on Io, resulting in a fair amount of brand new real estate on the surface of Io.
http://www.berkeley.edu/news/media/releases/2002/11/13_KeckII.html

These eruptions, as you see in the link, produced more new surface area than the entire surface area of many solar objects that we grace with the term "moon."  Something to think about...

This website also has some interesting stuff for you, in my opinion.
http://jove.geol.niu.edu/faculty/stoddard/IO/iogrl2.htm

However, these recent, 2001 events did not reform the ENTIRE surface of Io.  I'm putting things a bit strongly, just to make the point.  NASA's JPL webpage for Io gives the age of it's surface as "younger than a million years old," which is still INCREDIBLY young.
http://www2.jpl.nasa.gov/galileo/io/io_summary.html

This is JPL's website about Project Galileo's dealings with Io, in case you're interested.
http://www2.jpl.nasa.gov/galileo/gem/

By the way, Saturn's moon Titan is pretty young also, although people seem to be more interested in Io's youth.  Titan is interesting for other reasons).

As for Phobos, yes, it really is simply doomed.  It is going to crash into Mars in about 100,000,000 years, according to NASA.  That's a short period of time in astronomical terms, is that what you mean?  For a moon's future lifespan to be measured in millions, as opposed to billions of years, means that it will have a rather short total "lifespan," yes.
http://apod.nasa.gov/apod/ap041119.html

Keep Looking Up!
--Ed