[meteorite-list] Celebrating 35 Years of Charon

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 8 Jul 2013 13:16:37 -0700 (PDT)
Message-ID: <201307082016.r68KGbbE011222_at_zagami.jpl.nasa.gov>

http://pluto.jhuapl.edu/overview/piPerspective.php

The PI's Perspective: Celebrating 35 Years of Charon
A Giant Moon for the Ninth Planet
Dr. Alan Stern
July 5, 2013

This week the New Horizons mission team is celebrating the 35th
anniversary of the discovery of Pluto's largest and "first" moon,
Charon. This discovery was made in 1978 by U.S. Naval Observatory
astronomers James Christy and Robert Harrington, working in Flagstaff,
Ariz., and Washington, D.C.

Charon, whose discovery was first announced on July 7, 1978, orbits
about 19,400 kilometers (12,500 miles) from Pluto and has a diameter of
about 1,207 kilometers (750 miles) - about the width of Texas. At half
the diameter of Pluto, Charon is the largest moon relative to its planet
in our solar system.

Charon's reflective but almost colorless surface is covered by water
ice, and may contain traces of ammonia or ammonium as well. Its interior
is much less rocky than Pluto (which is nearly 70-percent rock). By
contrast, Charon's interior exhibits a nearly 50-50 combination of rock
and water ice. And unlike Pluto, Charon has no substantial atmosphere.

The historic discovery of Charon ushered in the modern understanding of
Pluto as both a double planet and the product of a giant collision that
formed the system in much the same way as the Earth-Moon system was formed.

We now know that Charon, once thought to be Pluto's only moon, orbits
Pluto with at least four much smaller moons: Nix, Hydra, Kerberos and
Styx, all of which, like Charon, orbit in circular paths and in Pluto's
equatorial plane.

>From Charon, Pluto looms large in the sky - more than 14 times as wide and
200 times as big of an area as the Earth's moon appears in our sky. And
at "full Pluto," Charon's night side is about 50-percent brighter than a
full moon in Earth's nighttime sky.

New Horizons is on course to fly by and make the first reconnaissance of
the Pluto system just two years from now, in July 2015. When it does,
the spacecraft will turn these moons and their parent planet Pluto from
points of light into well-mapped worlds, chart their compositions in
exquisite detail, explore Pluto's atmosphere, search for other moons and
rings, and make many other observations as well.

We're pretty excited to see Charon explored and its appearance revealed
in just two years, and hope you are too.

That's it for now. Until I write again, I hope you'll keep on exploring
- just as we will!
Received on Mon 08 Jul 2013 04:16:37 PM PDT