When astronauts explore Mars they will not survive without special suits to protect them against what is to all intents and purposes a hostile environment. Mars does not have a magnetosphere to protect it from radiation, or meteors and micro meteors, and while summer daylight temperatures are known to reach as high as 70 degrees Fahrenheit, or 26 degrees Celsius, the nighttime winter temperatures fall as low as -135 degrees Celsius.
It has become evident that dust devils are quite common on Mars during the summer months. These are not the whispy little whirlwinds of Earth's barren regions, but towering columns of wind many times the size of Earth's tornados whipping dust and sand around at over 70 miles per hour. It is becoming clear that they are more common than previously supposed and they are seen to occur at all latitudes on the planet. Many of these dust devils are huge, and these can be photographed from orbit.
According to William M. Farrell of NASA's Goddard Space Flight Center, the moving dust and sand particles of a dust devil may be electromagnetically charged because the smaller dust particles tend to charge negative, taking away electrons from the larger sand grains. This can cause arcing, which can damage sensitive electronic equipment and which can also cause radio interference. While the wind itself might not be too threatening at Mars' atmospheric pressure, which is about 1 percent that of Earth's atmospheric pressure at sea level, the high speed particles flying around might compromise the integrity of sensitive equipment and environment suits.
The thin atmosphere of Mars is 95 percent carbon dioxide. It is a very dry environment, and it is known that the dryness of a hot climate is a major contributing factor to the preservation of the ancient mummies found in the pyramids of Egypt. This does not necessarily mean that an unclothed dead body lying on Martian ground would be similarly preserved, however. It is probable that unprotected remains abandoned on the Martian surface would gradually disappear within a surprisingly fast time frame compared with Earth, probably within a few weeks.
The dry Martian air will very quickly dehydrate an unprotected dead body, and since most of our makeup is water, that would substantially reduce the body's mass. This process of desiccation represents the first step in the body's gradual disappearance.
The constant cycle of overnight contraction by freezing and daytime expansion by warming would begin the breakup of the brittle, desiccated remains. This deconstitution would be facilitated by erosion from radiation and micro meteor impacts. Dust devils would finish the work of dissipating the remaining residue as the assault of high speed dust and sand particles scour away what is left of the body. It is likely that the soft tissue will disappear within a week and the skeletal remains within a few weeks more. Mars is not kind to life - or death.