From: TerryMoselaol.com
Date: Fri, 3 Mar 2006 18:55:49 EST
Subject: Jupiter's new Red Spot, Asteroid impact threat

Hi all,
 
1. Jupiter has developed a new Red Spot! Only about half the size of the  one 
we know and love so well, but nevertheless, a really fascinating  development!
"Christopher  Go of the Philippines  photographed it on February 27th using 
an 11-inch telescope and a CCD camera:  



Above: Red  spots on Jupiter, photographed by amateur astronomer Christopher 
Go on Feb.  27, 2006. 
The  official name of this storm is "Oval BA," but "Red Jr." might be better. 
It's  about half the size of the famous Great Red Spot and almost exactly the 
same  color. 
Oval  BA first appeared in the year 2000 when three smaller spots collided 
and merged.  Using Hubble and other telescopes, astronomers watched with great 
interest. A  similar merger centuries ago may have created the original Great 
Red Spot, a  storm twice as wide as our planet and at least 300 years old. 
     
At  first, Oval BA remained white - the same color as the storms that combined 
to  create it. But in recent months, things began to change:  
"The  oval was white in November 2005, it slowly turned brown in December 
2005, and  red a few weeks ago," reports Go. "Now it is the same color as the 
Great Red  Spot!" 
"Wow!"  says Dr. Glenn Orton, an astronomer at JPL who specializes in studies 
of storms  on Jupiter and other giant planets. "This is convincing. We've 
been monitoring  Jupiter for years to see if Oval BA would turn red - and it 
finally seems to be  happening." (Red Jr? Orton prefers "the not-so-Great Red 
Spot.") 
Why  red? 
Curiously,  no one knows precisely why the Great Red Spot itself is red. A 
favorite idea is  that the storm dredges material from deep beneath Jupiter's 
cloudtops and lifts  it to high altitudes where solar ultraviolet radiation - via 
some unknown  chemical reaction - produces the familiar brick color.  
"The  Great Red Spot is the most powerful storm on Jupiter, indeed, in the 
whole solar  system," says Orton. The top of the storm rises 8 km above 
surrounding clouds.  "It takes a powerful storm to lift material so high," he adds. 



Above: Hubble images detail the birth of oval BA in 1997-2000.  
Oval  BA may have strengthened enough to do the same. Like the Great Red 
Spot, Red Jr.  may be lifting material above the clouds where solar ultraviolet 
rays turn  "chromophores" (color-changing compounds) red. If so, the deepening 
red is a  sign that the storm is intensifying. 
"Some  of Jupiter's white ovals have appeared slightly reddish before, for 
example in  late 1999, but not often and not for long," says Dr. John Rogers, 
author of the  book "Jupiter: The Giant Planet," which recounts telescopic 
observations of  Jupiter for the last 100+ years. "It will indeed be interesting to 
see if Oval  BA becomes permanently red." 
See  for yourself: Jupiter is easy to find in the dawn sky. Step outside 
before  sunrise, look south and up.  Jupiter outshines everything around it. Small 
 telescopes have no trouble making out Jupiter's cloudbelts and its four 
largest  moons. Telescopes 10-inches or larger with CCD cameras should be able to 
track  Red Jr. with ease. 
What's  next? Will Red Jr. remain red? Will it grow or subside?"
 
-  Definitely worth a look! 
 
2.  "Asteroid 2004 VD17  Classed as Torino Scale 2  
STATUS REPORT
Date Released: Wednesday, March 1,  2006
Source: Jet Propulsion Laboratory    
At the end of February, orbital  calculations for near-earth-asteroid (NEA) 
2004 VD17 indicated that the risk of  an impact within the next century 
(specifically on May 4,  2102) was  higher than that of any other known asteroid. The 
probability, based on 687  telescopic observations spanning 475 days, is 
listed on the NASA/JPL NEO Program  webpage as a bit less than 1 in 1000. This 
probability, while small, raises the  possible 2102 impact to a Torino scale 
value of 2 (meriting  attention from astronomers), which is higher than any other 
asteroid. (Note: the  impact probability for 1950 DA is larger, but since this 
hazard is not realized  until 2080, it falls outside the one-century range of 
the Torino scale).   
Judging from its  brightness, NEA 2004 VD17 has a nominal diameter near 500 m 
and a mass of nearly  a billion tons. While below the threshold for a global 
catastrophe, the nominal  impact energy of more than 10,000 megatons is 
comparable to all the world's  nuclear arsenals. There are no radar observations 
available, and the asteroid  has not been characterized in any detail, so all 
these numbers should be taken  as approximate.  
For comparison, NEA  Apophis (formerly 2004 MN4) is currently listed on the 
NEO webpage as Torino  scale 1, with an impact probability on April 13, 2036, 
of about 1 part in 5000.  Apophis is also smaller, with a nominal diameter of 
300 m and mass of less than  100 million tons. These are the only two asteroids 
currently with a Torino Scale  listing of greater than 0.  
Fortunately, it is nearly  a century before the close pass from VD17. This 
should provide ample time to  refine the orbit and, most probably, determine 
that the asteroid will miss the  Earth. On the other hand, there are no near-term 
opportunities for additional  observations, so VD17 will probably remain at 
Torino scale 2 for quite some  time. All  the above information is taken from 
the NASA/JPL NEO Program Office webpage at  
http://neo.jpl.nasa.gov. 
 
T.  M.'s Comment: This may well be headlined by the media, as they love a 
good  scary headline! But don't be too alarmed! Due to a statistical  anomaly, 
the calculated risk of an impact often increases from a very low level,  to a 
higher level, before further observations refining the orbit then reveal  the 
risk to be actually zero. 
    This is very hard to explain without a diagram, but in very simple  terms 
the predicted position of the asteroid as it crosses the Earth's  orbit on a 
certain date is an 'uncertainty ellipse', because we don't know  the 
asteroid's orbit really well yet. If the Earth's position on that date,  which is known 
very accurately, lies within that ellipse, then the relative  cross-sectional 
area of the Earth to the size of the ellipse gives the  probability of an 
impact - say 1:5,000. Further observations then refine the  orbit of the 
asteroid, so the new calculated uncertainty ellipse is smaller. But  if the Earth 
still lies within that ellipse, then the probability of an impact  goes up, 
because the ratio of Earth size to ellipse size has got smaller -  say 1:2,000. But 
what usually happens then is that the next refinement of  the orbit reduces 
the size of the ellipse even further, to the point where the  Earth now lies 
outside the ellipse, so the probability of collision goes to  zero.
    Obviously this is not certain at this stage, but don't be worrying about 
your  children or grandchildren just yet!
 
Clear  skies,
 
Terry  Moseley

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