You are here

More Moon and Mars

June 7, 2014

The Moon stages the first of two especially close encounters with other astronomical bodies this evening. The bright orange planet Mars is quite close to the upper right of the Moon as night falls. The star Spica is off to their left — the Moon’s next target.

Mars is the fourth planet from the Sun — an average of about 50 million miles farther from the Sun than Earth is. At that distance, Mars receives less than half as much sunlight as Earth does. Not surprisingly, that makes Mars a lot colder than Earth. Temperatures in the thin Martian atmosphere seldom climb above freezing, even in summer. And during winter nights, they can bottom out at more than 200 degrees below zero Fahrenheit.

Mars is tilted at about the same angle that Earth is, so it has the same cycle of seasons. The seasons are more extreme than here on Earth, though, because Mars’s distance to the Sun varies by quite a bit. Mars is closest to the Sun when it’s summer in the southern hemisphere, and farthest when it’s winter. So southern summers are warmer than those in the north, while southern winters are much colder.

The cold conditions create ice caps at the planet’s poles. But much of their ice vaporizes at the start of summer. The water vapor in the caps can form clouds — and can even produce snow. And the escaping gases can also stir up dust storms — some of which can eventually cover the entire planet.

We’ll talk about the Moon and Spica tomorrow.

Script by Damond Benningfield, Copyright 2014

Get Premium Audio

Listen to today's episode of StarDate on the web the same day it airs in high-quality streaming audio without any extra ads or announcements. Choose a $8 one-month pass, or listen every day for a year for just $30.