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Mars Compared to Earth

Mars Compared to Earth. Image credit: NASA/JPL

How Big is Mars Compared to Earth. Image credit: NASA/JPL

In many ways, Mars is very similar to Earth, but it’s also different in many ways. Let’s take a look at Mars compared to Earth.

Science fiction has built up Mars to be a twin planet of Earth. Sure, it’s colder and red, but it probably seems very similar to Earth, right? Well, Mars is actually a tiny little world. The diameter of Mars is 6,800 km across. This is 53% the diameter of Earth. And then consider the mass of Mars. It has only 10% the mass of Earth. Because of the small diameter and low mass, the surface gravity on Mars is only 38% the gravity on Earth. If your bathroom scale read 100 kg on Earth, it would only read 38 kg on Mars.

Mars and Earth are very similar in terms of their day length. A day on Mars lasts 1.03 Earth days. So humans could actually probably adapt to the day length on Mars. And the axial tilt on Mars is 25.19 degrees. Very close to Earth’s 23.5 degree tilt. This means that Mars has seasons which are very similar to Earth’s. Of course, since a year on Mars lasts about twice as long as an Earth year, the seasons are twice as long.

Don’t try to explore Mars without a spacesuit; you wouldn’t last very long. There are two major reasons why the climate on Mars is hostile to life as we know it. Temperatures on Mars can dip down to -87 degrees C, and rarely get above 0 degrees C. But the biggest issue is the lack of an atmosphere. The atmosphere of Mars is less than 1% the thickness of Earth’s atmosphere. Furthermore, it’s made up of 95% carbon dioxide – this is poisonous for us humans to breathe.

In some ways, Mars compared to Earth is actually quite similar, but in most ways, Mars is a totally different world; not suitable for humans to live on its surface without our technology.

We have written many articles about Mars here on Universe Today. Here’s an article about how difficult it will be to land large payloads onto the surface of Mars, and here’s an article about the Mars methane mystery.

If you’d like more info on Mars, check out Hubblesite’s News Releases about Mars, and here’s a link to the NASA Mars Exploration home page.

We have recorded several podcasts just about Mars. Including Episode 52: Mars and Episode 92: Missions to Mars, Part 1.

NASA Solar System Exploration: Earth and Mars Comparison Chart


Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

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