The first step in understanding the possibility of past or present life on Mars is to determine whether the red planet ever had environmental conditions able to support life. Now that NASA's two Mars Exploration Rovers, Spirit and Opportunity, have found compelling evidence that liquid water once persisted on the surface of Mars, scientists hope to determine if other things necessary for life were also present. With a single rover bigger than both the Viking landers sent to Mars in the 1970s, Mars Science Laboratory looks for chemical elements that are the building blocks of life. These building blocks include six elements necessary to all life on Earth: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.
Life requires small amounts of other elements, such as iron, along with sources of energy. On Earth, this energy comes from sunlight or from electrons moving back and forth between elements and compounds in nature. Life also requires a stable enough environment to get a foothold without being eradicated by natural hazards such as volcanic explosions or excessive ultraviolet radiation. The Mars Science Laboratory is studying carbon and water cycles on the planet through its history. That is, it seeks to determine in what form and amount carbon and water is stored on the planet or in its atmosphere and how that may have changed through time.
[more on Goal 1 for the entire Mars Exploration Program]
Mars Science Laboratory is characterizing Mars' ancient climate and climate processes for the lower and upper atmosphere. In the past, a warmer Mars might have supported a thicker, wetter atmosphere. But now, with its thin, cold atmosphere, much of the water on Mars has left the surface and atmosphere. Most of it is probably trapped under the surface, either as ice or possibly in liquid form if any exists near a heat source on the planet, such as a volcanic "hot spring." An earlier thicker, wetter atmosphere may have provided better environmental conditions for supporting microbial life in Mars' early history.
Mars Science Laboratory allows scientists to determine more precisely the composition of the Martian atmosphere, for instance, by measuring the stable isotopes of elements such as carbon. (Isotopes are atoms of the same element that have different masses because they have a different number of neutrons in the nucleus.) Most elements of biological interest have two or more stable isotopes. Organisms often selectively use particular isotopes based on their availability and mass. Environmental conditions also affect the availability of various isotopes. Mars Science Laboratory looks for biosignatures - signs of life - such as abrupt changes in isotopic abundance that might be associated with life, and investigates the composition of rocks, soils, and land forms that might be linked with changes in the planet's atmosphere over time.
Mars Science Laboratory is studying Martian weather patterns and characterizing the distribution of water, carbon dioxide, and hydrogen in the atmosphere and near the surface. It also measures surface radiation, including cosmic rays, solar protons, and neutrons bombarding the planet from space.
[more on Goal 2 for the entire Mars Exploration Program]
A record of Mars' history is folded in the layers of the martian surface -- in essence, geology's version of tree rings. Mars Science Laboratory studies the rock and soil record in order to understand the geologic processes that created and modified the martian crust and surface through time. In particular, it looks for evidence of rocks that formed in the presence of water.
[more on Goal 3 for the entire Mars Exploration Program]
By demonstrating an ability to land large, heavy payloads on the surface, Mars Science Laboratory paves the way for sending equipment and the huge infrastructure needed by any human explorers of the future. Experience in precision landing techniques also provides the first early steps in developing an ability to send astronauts to a given location safely and reliably.
A better understanding and characterization of radiation levels at the surface of Mars will help mission planners understand potential hazards faced by any future astronaut crews and design methods for protecting their health.
[more on Goal 4 for the entire Mars Exploration Program]