MadSci Network: Earth Sciences
Query:

Re: Describe kind, quantity, & impact of cosmic debris falling on earth?

Date: Fri Jun 22 13:41:35 2001
Posted By: Jennifer Anderson, Grad student, Geological Sciences, Brown University
Area of science: Earth Sciences
ID: 992230581.Es
Message:

Earth certainly is bombarded by a large amount of material from outer space.  
This material can come in all different sizes, from the largest meteorites 
and comets to the smallest grains of dust.  In general, the odds of a large 
meteorite hitting the Earth are extremely small.  A meteorite the size of 
the one that killed the dinosaurs will only fall to Earth every 100 million 
years or so.  And most meteorites that start out larger in outer space (10’s 
of tons or smaller) will be broken up as they pass through the Earth’s 
atmosphere, so that when they reach the surface they won’t do too much 
damage.  Therefore, although there is big stuff that occasionally falls to 
Earth, this is not the main source of cosmic debris.  

Rather, the material that we sweep up every day from outer space is most 
likely to be extremely small, sand grain size or smaller dust.  At night, 
when you watch a meteor shower and there are many streaks of light passing 
across the sky, you are actually watching sand grains burn up in our 
atmosphere.  The friction from the atmosphere rubbing on the sand grain as 
it moves very quickly is hot enough to burn that sand grain up and we see 
the heat as a meteor.  The Earth captures about 40,000 tons of dust from 
outer space each year (so you can see that the big stuff is hardly important 
compared to all the little stuff).  These dust particles are usually very 
rich in carbon and otherwise contain tiny bits of minerals that are commonly 
found in meteorites.  

Billions of years ago, when the solar system was still very young, there was 
a lot more material floating around in our solar system that could be swept 
up onto the Earth and so the numbers above would have been much higher 
nearer the beginning of the solar system.  Back then, it might have been 
possible for an extremely large impact to affect the Earth’s rotation or 
length of day.  And, of course, a very large impact, like the one that led 
to the extinction of the dinosaurs, can have huge and global effects on life 
on Earth.  However, even the meteorite that caused the dinosaur’s extinction 
was not big enough to affect the Earth’s gravity, rotation or length of 
year. 

For more information on the cosmic dust that falls to Earth, technically 
termed "Interplanetary Dust Particles" or IDPs, check out this website from 
Washington University in St. Louis.  There are some great images of what 
these particles look like:
 http://
stardust.wustl.edu/IDPIntro.html



Current Queue | Current Queue for Earth Sciences | Earth Sciences archives

Try the links in the MadSci Library for more information on Earth Sciences.



MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci


MadSci Network, webadmin@www.madsci.org
© 1995-2001. All rights reserved.