Mars is farther from the Sun than the Earth, so, as you would expect, the temperature of Mars is colder. For the most part it is very cold on Mars. The only exception is during the summer days close to or at the equator. Even at the equator, the night time temperatures fall well below zero. On those summer days, it can be around 20 degrees Celsius then plummet to -90 C at night.
Mars follows a highly elliptical orbit, so temperatures vary quite a bit as the planet travels around the Sun. Since Mars has an axial tilt similar to Earth’s(25.19 for Mars and 26.27 for Earth), the planet has seasons as well. Add to that a thin atmosphere and you can see why the planet is unable to retain heat. The Martian atmosphere is over 96% carbon dioxide. If the planet had an atmosphere to retain heat, the carbon dioxide would cause a greenhouse effect that would heat Mars to jungle like temperatures.
Scientist know the current temperature of Mars, but what about the past. Rovers and orbiters have returned images that indicate erosion patterns that can only be caused by liquid water. That would seem to indicate that Mars was once much warmer and wetter. Here on Earth, those features would have been covered in soil after a few million years. So, was Mars warmer just a few million years ago? No, Mars has been a frigid planet for at least 3 billion years and some scientist believe it has been frozen for 4 billion years. The erosion features have not disappeared because there is no current liquid water or plate tectonics to change the landscape. What wind there is, does not seem strong enough to further erode the surface.
Tracking the presence of warmer weather and liquid water on Mars is important for a few reasons. One is that liquid water is essential for the evolution of life as we know it. Some scientists still hold out hope that there is microbial life deep beneath the surface where it is warmer and water may exist. Secondly, if humans are to ever explore the planet, they would need a water source. A human mission would take nearly two years to complete and storage space would be limited. Water ice may be melted upon arrival then purified, but finding a supply of liquid water would be even more expedient.
The temperature of Mars is a minor obstacle to early human exploration, while water is more pressing. Current spacesuits would survive the surface temperatures. Now, all we have to do is find a way to get there and back without having to spend two years in a cramped modern spacecraft.
Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.