EarthSky offers readers “updates on your cosmos and world.” Today, they posted a guide to viewing the five visible planets in October 2015. And which planets might these be?
Of the eight planets in our Solar System, Mercury is both smallest and closest to the Sun. This past April, the spacecraft MESSENGER crashed into Mercury after orbiting the planet for four years, twice as long as the mission was originally planned.
In our night sky, only the Moon is brighter than Venus, the second planet from the Sun. Venus has the slowest rotation of any planet; it completes an orbit of the Sun more quickly than it completes a full rotation on its axis. MESSENGER did two fly-bys of Venus on its way to Mercury, and NASA has a lander mission planned for the future. It’s a lot like Earth, but the surface is drier and much hotter, with an atmospheric pressure 92 times that of Earth.
On Monday, NASA made a huge announcement: chemical evidence of liquid water on Mars. The rovers Opportunity and Curiosity are currently exploring the surface of Mars, but they won’t be sipping that water any time soon, for fear of contaminating it with whatever they picked up on their trip through space.
Made of mostly hydrogen and orbited by dozens of moons, Jupiter is the largest and most massive (by a long shot!) planet and sits fifth from the Sun. NASA has done several fly-bys, and the spacecraft Galileo orbited Jupiter for seven years. Even before Galileo got there, it witnessed the impact of Comet Shoemaker-Levy 9 up close. And what of that red spot on Jupiter’s surface? It’s a storm bigger than Earth, though Hubble Telescope observations suggest it’s shrinking.
If you’ve ever seen Saturn clearly through a telescope, as we did during the Launch Pad Astronomy Workshop for writers, you know those rings of ice, rock, and dust are as distinct as and more amazing than depicted in any book. Saturn is a gas giant like Jupiter but 318 less massive; still, it’s 95 more massive than Earth. Several spacecraft have done fly-bys, and Cassini entered orbit around Saturn in 2004, and it’s still doing its work after more than a decade, even though the primary mission ended in 2008.