Mars has been known since antiquity. In contrast to stars which remain in fixed patterns known as constellations, Mars is one of five star-like objects easily visible with the naked eye that change position over time.

By 1877, scientists had determined the orbit, rotational period and other information about Mars, however some basic questions remained to be answered. Observers had noticed that there were white spots near the poles (which we now call polar caps), dark areas (which we now call maria), various markings (which became known as canals), and white spots (which were interpreted as clouds and proved that Mars had an atmosphere). However misconceptions about the polar caps, maria, canals and the atmosphere became established.

In particular, Percival Lowell (a Boston astronomer) simultaneously created intense public interest in Mars, starting asking difficult questions and perpetuated numerous mistaken ideas.

Many of these misconceptions and mistaken ideas would persist until the 1960’s when unmanned spacecraft visited Mars. Those spacecraft have returned photographs and other data that showed there were no canals, and gave us a better understanding of the maria, polar caps and the atmosphere. However a fundamental question remains unanswered: Does Mars have life or did it have life at some point in the past? Some (but not all) scientists think Mars was inhabited by microorganisms billions of years ago, but even if there was life on Mars, it is not clear if descendents of these microorganisms still live on Mars.

Observing Mars

Mars (Valles Marineris).

Mars is easy to observe with the unaided eye. If you do this, you will notice that Mars undergoes dramatic changes in brightness and color over the course of a two year cycle. Once during the two year cycle, Mars will stop, reverse direction, stop again and continue in the original direction.

If you want to see more detail, you need a telescope. The best time to observe Mars is beginning about a month before opposition (which occurs once during the two year cycle) and ending about a month after opposition. The rest of the time, it is difficult to see any detail. Every 15 years there is an exceptionally good opposition; the last one was in 2003. The 2003 opposition was better than most, the last time Mars was this close to the Earth was about 100,000 years ago, the next time it will be this close will be in 284 years.

Details that are easy to see in a telescope are the polar caps and the maria. Other details, such as the moons, are harder to see.

More on Mars