The Mars Science Laboratory mission has four main scientific objectives:
Determine whether life ever arose on Mars.
The first clues that will indicate whether life ever arose on Mars are linked to environmental conditions that prevailled. The last missions to Mars (Mars Exploration Rovers and Mars Express) have demonstrated that liquid water has been present soon after the planet formation and during a few million years. Scientists now hope to determine if other elements which have been able to combine for life to arise are still present on Mars. MSL is searching for some of these chemical elements: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.
Life as we know it also uses other elements in small quantities such as iron, sodium, calcium, manganese, etc. At last, life requires sources of energy. On Earth, this energy probably came at first from oxydo-reduction chemical reactions. Nowadays, it mainly comes from the Sun through photosynthesis. Life also requires a stable enough environment to resist natural hazards such as volcanic explosions or major meteoritic impacts. Lastly, life should be shielded from ultraviolet radiations and powerful oxidizing agents; it subsists if temperature does not vary too much and if the water stays avalaible in sufficient quantities. The mission is designed to study carbon and water cycles on the planet through its history. The MSL instruments are trying to determine under which form and in which quantities carbon and water are stocked on the planet and in the atmosphere.
Characterize the climate of Mars.
Mars Science Laboratory is characterizing Mars' ancient climate and climate processes for 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. An earlier thicker, wetter atmosphere may have provided better environmental conditions for supporting microbial life in Mars' history.
Thanks to MSL, we are learning more about the Martian atmosphere's composition, including by measuring the stable isotopes of elements such as carbon. 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. MSL is looking for biosignatures–signs of life–such as abrupt changes in isotopic abundance that might be associated with life, and investigating the composition of rocks, soils, and land forms that might be linked with changes in the planet's atmosphere over time.
MSL 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 radiations, including cosmic rays, solar protons, and neutrons bombarding the planet from space.
Characterize the geology of Mars.
A record of Mars' history can be found in the layers of the Martian surface–in essence, the geological equivalent of tree rings. MSL has been designed to study the rock and soil record in order to understand the geological processes that created and modified the Martian crust and surface through time. In particular, it is looking for evidence of rocks that formed in the presence of water.
Prepare for human exploration.
By demonstrating an ability to land large, heavy payloads on the surface, MSL is paving the way for sending equipment and the huge infrastructure needed by future human explorers. Experience in precision landing techniques will also provide the first early steps in developing an ability to send astronauts to a given location safely and reliably.
Mars Science Laboratory was launched on 26 November 2011. It arrived on 6 August 2012. The planned primary launch period was chosen based on the availability of the Mars Reconnaissance Orbiter (MRO) and direct-to-Earth (DTE) entry, descent, and landing communication strategies.
NASA's Kennedy Space Centre in Florida selected at the beginning of June 2006, Lockheed Martin Commercial Launch Services Inc. to supply an Atlas V launcher for Curiosity. The ATLAS V launch vehicle has a five-meter fairing. At launch, the spacecraft mass was around 3900 kilograms.
The cruise phase began soon after separation from the launch vehicle when the spacecraft completed the launch phase. Cruise ended when the spacecraft was 45 days from entry into the Lartian atmosphere, when the approach phase started.
Major activities during the cruise phase included the following:
- health checks and upkeeping of the spacecraft in its cruise configuration
- monitoring and calibrating the spacecraft and sub-systems
- attitude correction turns (spins to maintain the antenna pointing toward Earth for communications and the solar panels pointed toward the Sun for power)
- navigation activities, including trajectory correction manoeuvres, for determining and correcting the vehicle's flight path and for training navigators prior to approach
- preparation for entry, descent, and landing and surface operations, including communication tests used during entry, descent, and landing.
To ensure a successful entry, descent, and landing, engineers began intensive preparations during the approach phase, 45 days before the spacecraft entered the Martian atmosphere. It lasted until the spacecraft entered the Martian atmosphere, which extends 3500 kilometres as measured from the centre of the Red Planet.
The activities that engineers typically focus on during the approach phase include:
- the final trajectory correction manoeuvres, which were used to make final adjustments to the spacecraft's incoming trajectory at Mars
- attitude pointing updates, as necessary, for communications and power
- frequent "Delta DOR" measurements that monitor the spacecraft's position and ensure accurate delivery
- start of the entry, descent, and landing behaviour software, which automatically executed commands during that phase
- entry, descent, and landing parameter updates
- spacecraft activities leading up to the final turn to the entry attitude and separation from the cruise stage
- the loading of surface sequences and communication windows needed for the first several sols (a "sol" is a Martian day).
Entry, Descent, and Landing
The entry, descent, and landing (EDL) phase began when the spacecraft reached the Martian atmosphere, about 125 kilometres above the surface, and ended with the rover safe and sound on the surface of Mars.
Entry, descent, and landing for the Mars Science Laboratory mission included a combination of technologies inherited from past NASA's Mars missions, as well as exciting new technologies. The sheer size of the rover Curiosity (900 kilograms) precluded it from taking advantage of an airbag-assisted landing. Instead, MSL used the sky crane touchdown system, which was capable of delivering a much larger rover onto the surface. It placed the rover on its wheels, ready to begin its mission.
The new entry, descent and landing architecture, with its use of guided entry, allowed for more precision. Where the Mars Exploration Rovers could have landed anywhere within their respective 150 by 20 kilometers landing ellipses, Mars Science Laboratory landed within a 20-kilometre ellipse! This high-precision delivery has opened up more areas of Mars for exploration and potentially has allowed scientists to "virtually" roam where they have not been able to before. The entry, descent, and landing sequence breaks down into four parts:
- Guided Entry - The spacecraft was controlled by small rockets during descent through the Martian atmosphere, toward the surface.
- Parachute Descent - Like Viking, Pathfinder and the Mars Exploration Rovers, the Mars Science Laboratory was slowed by a large parachute.
- Powered Descent - Again, rockets controlled the spacecraft's descent until the rover separated from its final delivery system, the sky crane.
- Sky Crane - Like a large crane on Earth, the sky crane system lowered the rover to a "soft landing"–wheels down–on the surface of Mars.
Narrowing of Mars rover, Curiosity, landing site by NASA
Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS
The surface operations phase covers the rover's time on Mars. After reaching the surface of the red planet, Curiosity is being designed to have a primary mission time of one Martian year. That is, it would continue to operate for at least 687 Earth days, surviving at least one Martian winter in the process. MSL was designed to have higher clearance and greater mobility than any previous rover sent to Mars, traveling a distance of 5 to 20 kilometres from its landing site. While exploring Mars, the rover is collecting, grinding, distributing, and analyzing approximately 70 samples of soil and rock.