Every day a robotic rover about the size of a small car wakes up and makes its next move across the surface of Mars. It's called the Curiosity Mars Science Laboratory rover, exploring around Mount Sharp at the center of Gale Crater (an ancient impact site) on the Red Planet. It's one of two working rovers on the Red Planet. The other is the Opportunity rover, perched on the west rim of Endeavour Crater. The Mars Exploration Rover Spirit stopped working and is now silent after several years of exploration on its own.
Each year, Curiosity's science team celebrates another full Martian year of exploration. A Mars year is longer than an Earth year, roughly 687 Earth days, and Curiosity has been doing its job since August 6, 2012. It has been a momentous time, revealing dazzling new information about Earth's neighbor in the solar system. Planetary scientists and future Mars mission planners are interested in conditions on the planet, particularly its ability to support life.
The Search for Martian Water
One of the most important questions the Curiosity (and other) missions wants to answer is: what is the history of water on Mars? Curiosity's instruments and cameras were designed to help answer that.
It was fitting then, that one of Curiosity's first discoveries was an ancient riverbed running underneath the rover's landing site. Not far away, at an area known as Yellowknife Bay, the rover dug into two slabs of mudstone (rock formed from mud) and studied samples. The idea was to look for habitable zones for simple life forms. The study gave a definite "yes, this could have been a place hospitable to life" answer. Analysis of the mudstone samples showed that they were once at the bottom of a lake filled with water rich in nutrients. That's the kind of place where life could have formed and flourished on the early Earth. If Mars had living organisms, this would have been a good home for them, as well.
Where Did the Water Go?
One question that keeps coming up is, "If Mars had a lot of water in the past, where did it all go?" The answers suggest a range of places, from frozen underground reservoirs to the ice caps. Studies by the MAVEN spacecraft orbiting the planet strongly support the idea that some episode of water loss to space occurred. This changed the planet's climate. Curiosity has measured various gases in the Martian atmosphere and has helped Mars scientists figure out that much of the early atmosphere (which was probably wetter than now) escaped to space. More recent studies have revealed underground ice on Mars, and possibly salty meltwater just beneath the surface in some areas.
Rocks tell a fascinating story of Mars water. Curiosity has determined of the ages of Martian rocks, and how long a rock has been exposed to harmful radiation. Rocks in direct contact with water in the past tell scientists more details about water's role on Mars. The big question: when did water flow freely across Mars is still unanswered, but Curiosity is providing data to help answer it soon.
Curiosity has also returned important information about radiation levels on the Martian surface, which would be important for assuring the safety of future Mars colonists. Future trips range from one-way missions to long-term missions that send and return multiple crews to and from the Red Planet.
Curiosity is still running strong, despite some damage to one its wheels. That has led team members and spacecraft controllers to devise new study routes to accommodate the problem.The mission is one more step to the eventual human exploration of Mars. As with our exploration of Earth over the past centuries - using advance scouts - this mission and others, like the MAVENmission and India's Mars Orbiter Mission are sending back valuable word about the territory ahead, and what our first explorers will find.