1. One of these things is not like the other!!

2. http://upload. wikimedia

3. MERCURY

4. MERCURY Temperatures range from -183 to +467 degrees Celsius
This is hot enough to melt metals
Mercury has been visited by two spacecraft, Mariner 10 and MESSENGER.
Mercury has a very thin atmosphere.

5. Radar observations of Mercury's north pole show evidence of water ice in the protected shadows of some craters.

6. VENUS

7. VENUS The first spacecraft to visit Venus was Mariner 2 in 1962.
It was subsequently visited by more than 20 others
Venus is sometimes regarded as Earth's sister planet
Temperature can get over 450 degrees but there is little change.

8. The pressure of Venus' atmosphere at the surface is 90 atmospheres (Earth=1)
It is composed mostly of carbon dioxide.
There are several layers of clouds many kilometers thick composed of sulfuric acid
Venus probably once had large amounts of water like Earth but it all boiled away. Venus is now quite dry.

9. MARS

10. Earth or Mars

11. MARS The first spacecraft to visit Mars was Mariner 4 in 1965.
Today there are 6 space craft exploring Mars.
While the average temperature on Mars is about -55 C, Martian surface temperatures range widely from -133 C to almost 27 C

12. Mars has permanent ice caps at both poles composed of water ice and solid carbon dioxide ("dry ice").
Mars has a very thin atmosphere
At some time in the past there was clearly some sort of fluid on the surface, most likely liquid water.
There may have been large lakes or even oceans