Skip to content

Cold on Mars

Heat and matter · level 1, lesson 6 of 6

A question to start

Is Mars a hot planet or a cold one? It is red, like fire. Does that mean it is hot?

The idea

Mars is very cold. Red does not mean hot: its red colour comes from rusty dust. Mars is farther from the Sun than Earth is, so it gets less warmth from sunlight, and its air is so thin that it cannot hold warmth in.

How cold? Mars Earth
Average temperature about −60 °C about 15 °C
Compared with a freezer (−18 °C) much colder much warmer
Earth 15 °C0 °Cfreezer Mars−60 °C

Nights on Mars are colder still. The Viking 1 lander measured about −89 °C at night and −31 °C in the day.

So rovers on Mars carry heaters. The rovers Spirit and Opportunity each had eight tiny heaters, each about the size of a small battery, and each giving out about as much warmth as a small torch bulb. Perseverance keeps its "brains" in a box called the warm electronics box.

Worked examples

1. A freezer. Your freezer is about −18 °C. An average place on Mars is more than three times as far below zero.

2. A Mars night. −89 °C is about five times as far below zero as your freezer.

3. A rover. Without heaters, its batteries and computer would get too cold to work.

Try it

  1. Is Mars hot or cold?
  2. Why is Mars red?
  3. Which is colder, a Mars night or your freezer?
  4. Why do rovers carry heaters?
Answers
  1. Very cold.
  2. Its dust is rusty.
  3. A Mars night, by a long way.
  4. To keep their batteries and computers warm enough to work.

Common mistake

"Red planets are hot." Colour does not tell you temperature. Mars is red because of rust, and it is far colder than Earth.

Where it leads