13 December 2012, 04:50 PM ET
Astronomer Giovanni Cassini discovered four of Saturn's moons, determined the distance from Earth to Mars and made successful measurements of longitude.
11 December 2012, 01:31 PM ET
Elon Musk founded SpaceX with ambitions to explore Mars.
06 December 2012, 04:02 PM ET
Viking 2 was the second NASA spacecraft to make a soft landing on Mars.
05 December 2012, 04:35 PM ET
Our first glimpse of Mars in 1964 revealed craters and a barren landscape.
04 December 2012, 05:52 PM ET
Although it eventually got stuck and stopped transmitting, the Spirit rover found evidence of water in Mars' past and paved the way for the more robust Curiosity.
03 December 2012, 05:22 PM ET
Mariner 2 revealed Venus' hot temperature and high surface pressure.
30 November 2012, 12:44 PM ET
Uranus is the smallest of the gas giants in the outer solar system.
30 November 2012, 12:39 PM ET
The distance to Uranus from Earth is more than a billion miles.
30 November 2012, 12:34 PM ET
The blue color of Uranus is caused by methane.
30 November 2012, 12:25 PM ET
Uranus is the coldest planet in the solar system.
30 November 2012, 12:21 PM ET
Uranus is one of two ice giants in the outer solar system.
30 November 2012, 12:18 PM ET
Light elements clumped together to form the gas giants.
30 November 2012, 12:14 PM ET
Discovered in 1781, the seventh planet was destined to cause snickers whenever someone says its name.
28 November 2012, 12:41 PM ET
The Chandra X-Ray Observatory has probed the origins of dark matter and revealed much about the parts of the universe we can't see visually.
27 November 2012, 01:10 PM ET
Mercury is the smallest planet, but it is very dense.
27 November 2012, 12:53 PM ET
Mercury is the sun's closest planet, but it has a bizarre orbit.
27 November 2012, 12:44 PM ET
Despite being closest to the sun, Mercury is not the hottest planet.
27 November 2012, 12:26 PM ET
The solar wind blasts the closest planet to the sun, leaving it with the thinnest atmosphere of all the planets.
27 November 2012, 12:14 PM ET
Mercury is a terrestrial planet with a rocky surface and metallic core.
27 November 2012, 12:03 PM ET
The smallest planet collected material from the solar nebula.
26 November 2012, 04:55 PM ET
Galileo was the first space probe to spend years observing the planet Jupiter and its moons
20 November 2012, 01:29 PM ET
Pluto is two-thirds as big as Earth's moon.
20 November 2012, 01:20 PM ET
The distance to Pluto changes because of the dwarf planet's odd orbit.
20 November 2012, 01:02 PM ET
Yes. Scientists think Pluto's atmosphere is mostly nitrogen.
20 November 2012, 12:51 PM ET
Pluto is one of the coldest bodies in the solar system.
20 November 2012, 12:37 PM ET
The dwarf planet is composed of rocky material and a great deal of ice.
20 November 2012, 12:31 PM ET
The dwarf planet formed a bit differently from the rest of the solar system.
19 November 2012, 04:52 PM ET
To this day, the photos taken by the Soviet spacecraft are the best we have from the cloudy planet.
16 November 2012, 06:41 PM ET
Venus is slightly smaller than Earth.
16 November 2012, 06:34 PM ET
Venus is the closest planet to Earth.
16 November 2012, 06:23 PM ET
The atmosphere of Venus is thick with clouds of carbon dioxide.
16 November 2012, 06:15 PM ET
Venus is the hottest planet in the solar system.