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The Mars year

Space and time · level 4, lesson 4 of 6

A question to start

You are 12 years old on Earth. How old would you be in Mars years? How often would you get a birthday?

The idea

Mars is farther from the Sun than Earth, and it moves more slowly, so it takes longer to go round. One trip, a Mars year, lasts about 687 Earth days, or 668.6 sols.

One year Mars Earth
In Earth days about 687 about 365.25
In the planet's own days about 668.6 sols about 365.25 days
In Earth years about 1.88 1

Scientists number Mars years too. Mars Year 1 began on 11 April 1955, at the start of northern spring on Mars. The date was picked so that a global dust storm watched in 1956 fell in Year 1. Mars Year 39 began on 30 September 2026.

Mars: once roundin 687 daysEarth: once roundin 365 days

Worked examples

1. Years. \(687 \div 365.25 \approx 1.88\): a Mars year is nearly two Earth years.

2. Your age. \(12 \times 365.25 = 4{,}383\) Earth days. \(4{,}383 \div 687 \approx 6.4\) Mars years.

3. Birthdays. A Mars birthday comes once every 687 Earth days, so about once every 1 year 10 months.

Try it

  1. About how many Earth days are in a Mars year?
  2. About how many sols are in a Mars year?
  3. When did Mars Year 1 begin?
  4. Someone is 30 Earth years old. About how old are they in Mars years?
Answers
  1. About 687.
  2. About 668.6.
  3. 11 April 1955.
  4. \(30 \div 1.88 \approx 16\) Mars years.

Common mistake

Mixing days and sols. A Mars year is 687 Earth days but 668.6 sols. Say which one you mean.

Where it leads