Mars, the fourth planet from the Sun, has long been a popular object of observation. It can be clearly seen in the night sky from Earth and has been studied since ancient times. Mars is a rocky planet with a diameter about half the size of Earth’s. Its surface is littered with impact craters and includes familiar features such as mountains, valleys, canyons, deserts, and polar ice caps. Mars's nickname, the Red Planet, comes from the iron oxide (rust) in its soil, which gives it a reddish appearance. The average surface temperature on Mars is about -63°C (-81°F), but its thin atmosphere contributes to extreme fluctuations in temperature from day to night. Although the current environment on Mars is harsh and inhospitable to life, there is evidence that it was once quite different and that liquid water may have existed on its surface.

As one of Earth's closest neighbors and a prime candidate for a world that could have supported life, Mars is an exciting scientific target and the planet most visited by spacecraft from Earth. Because of its proximity, it takes only 7 to 9 months for a spacecraft to reach it. Furthermore, there is a launch window every 26 months (when the alignment of Earth and Mars produces the best trajectory for a spacecraft). Compared to other key targets in the search for extraterrestrial life, such as Jupiter's moon Europa or Saturn's moon Titan, Mars is much easier to visit. Many types of missions—flybys, orbiters, landers, and rovers—have had the opportunity to explore the Red Planet. NASA's involvement in Mars exploration includes the Mariner and Viking programs in the 1960s and ’70s, Mars Pathfinder and Mars Global Surveyor (launched in 1996), Mars Odyssey (2001), Mars Express (2003), Mars Exploration Rovers (2003), Mars Reconnaissance Orbiter (2005), and Mars Science Laboratory (2011).

The flyover images seen in the videos were created from data collected by Mars Reconnaissance Orbiter (MRO), whose primary goals included global mapping, regional surveying, and high-resolution imaging of specific areas. MRO was equipped with several instruments, including cameras, spectrometers, and radar. The flyover videos were made using data captured by the HiRISE (High Resolution Imaging Science Experiment) instrument, which operates in visible and near-infrared wavelengths and can capture high-resolution images that distinguish features about one meter in size. Intensive computer processing translates these two-dimensional images into three-dimensional representations to create a digital terrain model (DTM). Made from images of an area that are captured from two different points in MRO’s orbit, a DTM can accurately describe elevation values and show features such as hills, valleys, and channels.

Using images like these, together with an understanding of geological processes on Earth, scientists can interpret such observations of distant worlds. Although no human has yet stepped foot on Mars, scientists are able to study it and form strong hypotheses using remotely gathered data. However, a future sample-return mission could bring rock and dust samples of Mars back to Earth for analysis, and humans may one day have the opportunity to visit the planet.

Print Background Essay