Earth's Atmosphere

Due to the increase in the different gasses in our atmosphere, the atmosphere is becoming more and more thinner and slowly merging with space at about 100 km. This boundary is known as the Stratosphere (Karman line). The atmosphere protects the earth from energetic X-rays as well as keeps the temperature at an average of 15 degrees. This is done by reflecting excess sunlight away from the earth.

BBC Bitesize

 

In basic terms the Earth's atmosphere protects the Earth from heating up and absorbing large amounts of different radiation such as x-rays, gamma rays etc. It also protects us from meteorites to an extent as when the meteorite enters the Earth's atmosphere most of the mass is burned reducing the size of the impact.
 

Gas:	Percentage in atmosphere:
Nitrogen	78%
Oxygen	21%
Argon	1%
Carbon dioxide (at present)	0.04%
Water vapour	1%

Pluto moons get mythical new names

The recently discovered fourth and fifth moons of Pluto now have official names: Kerberos and Styx.

(from NASA)

The names - referring to a three-headed dog and a river separating the living from the dead, ranked second and third in an international public vote.

The two moons, formerly known simply as P4 and P5, were only discovered in July 2011 and July 2012, respectively. Both were spotted by a team using the Hubble space telescope, led by Mark Showalter, senior scientist at the Seti Institute.

Vulcan was a suggestion made by William Shatner of the television show Star Trek - the name of the home planet of character Mr Spock. Although it was a clear winner among the votes, the IAU opted not to use it, on the grounds that it has been used elsewhere in astronomy and not sufficiently associated in mythology with Pluto, the ruler of the underworld.