28. The Martian atmosphere is very different from Earth’s.
The two most abundant elements in the solar system are hydrogen and helium, and they form the bulk of the composition of both the Earth and Mars. However, there are also many other elements in Earth’s atmosphere, many of which are created by the respiration of the organisms on Earth. For example, our atmosphere has enough oxygen for humans and animals to thrive because plants breathe in carbon dioxide and breathe out oxygen.
Mars, on the other hand, does not have plants to convert its carbon dioxide into oxygen. Fully 96 percent of its atmosphere is carbon dioxide, so there is no way that humans could live in those conditions. Furthermore, its atmosphere is 100 times less dense than Earth’s, so even if we could solve the oxygen problem, we would have a lot more challenges to overcome before living there.