• Question: how come the earth is the only planet with an atmosphere and gravity

    Asked by 799enek52 to Emma, Karla, Shane, Stephen, Yang on 14 Nov 2017.
    • Photo: Stephen Rhatigan

      Stephen Rhatigan answered on 14 Nov 2017:

      The Earth is not the only planet with an atmosphere and gravity. Any object with mass has a gravitational field. Even you and me. And a gravitational field is what allows a planet to keep an atmosphere.
      But gravity is a very weak force so in order for it to be noticeable an object must have a lot of mass – like a planet or a star. The more mass the greater the gravitational force.
      The Earth is more massive than Mars and so the force of gravity on Earth’s surface is greater than the force of gravity on the surface of Mars. So you weigh less on Mars than you do on Earth.
      The gravitational force of the sun is so strong that it keeps all the planets from flying off into space.
      Earth is the only planet in the solar system that has an atmosphere that is suitable for life – our atmosphere is mostly nitrogen and oxygen. Mars has an atmosphere but it is mostly carbon dioxide. The gravity on the moon is so weak that it can’t keep an atmosphere.

    • Photo: Karla Dussan

      Karla Dussan answered on 14 Nov 2017:

      @Stephen’s explanation is great. We can also mention that one of the properties of Earth that scientists would look in other planets would be having water and having a start around like our sun. At the beginning of the year, scientists discovered “solar system” with seven planets much in the fashion of our solar system. You can read more about it here — > https://www.nasa.gov/press-release/nasa-telescope-reveals-largest-batch-of-earth-size-habitable-zone-planets-around

    • Photo: Emma Hanley

      Emma Hanley answered on 14 Nov 2017:

      I think Stephen and Karla did a good job of answering. Just to add Earth’s atmosphere (78% nitrogen, 21% oxygen, 0.9% argon, and 0.03% carbon dioxide with very small percentages of other elements) atmosphere protects living things on Earth from the sun’s harmful ultraviolet radiation and helps sustain life of Earth