|Nation||United States of America (USA)|
|Objective(s)||Mars Landing and Rover|
|Spacecraft||Mars Science Lab (MSL)|
|Spacecraft Mass||8,583 pounds (3,893 kilograms)|
|Mission Design and Management||NASA / JPL|
|Launch Vehicle||Atlas V 541 (AV-028 + Centaur|
|Launch Date and Time||Nov. 26, 2011 / 15:02:00 UT|
|Launch Site||Cape Canaveral, Fla. / SLC-41|
- Curiosity demonstrated new heavy-load Mars landing technologies
Nov. 26, 2011: Launch
Aug. 6, 2012: Mars landing
Aug. 29, 2012: Curiosity began its first drive
In Depth: Curiosity (MSL)
NASA’s Mars Science Laboratory mission set down a large, 1,982-pound (899-kilogram), mobile laboratory—Curiosity Mars rover—at Gale Crater, using precision landing technology that made one of Mars’ most intriguing regions a viable destination for the first time.
Within the first eight months of a planned 23-month primary mission, Curiosity met its major objective of finding evidence of a past environment well suited to supporting microbial life.
The rover continues to study the geology and environment of selected areas on Mars.
Curiosity, part of NASA’s Mars Exploration Program, carries the most advanced complement of instruments ever sent to the surface of Mars. The rover is designed to scoop up soil and rocks and to investigate their formation, structure, and chemical composition in order to look for the chemical building blocks of life (carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur).
Curiosity is able to travel up to 295 feet (90 meters) per hour on its six-wheeled “rocker-bogie” system. The term "bogie" comes from old railroad systems. A “bogie” is a train undercarriage with wheels that can swivel to curve along a track. The term "rocker" comes from the design of the differential, which keeps the rover body balanced, enabling it to "rock" up or down depending on the various positions of the multiple wheels.
The rover is powered by a radioisotope power system to generate energy from the heat of plutonium’s radioactive decay. Curiosity’s operations depend heavily on the orbital communications capabilities of 2001 Mars Odyssey and Mars Reconnaissance Orbiter.
The robot was named “Curiosity” after a nationwide student contest involving more than 9,000 entries. The winning entry was submitted by Clara Ma, a sixth-grade student from Sunflower Elementary School in Lenexa, Kansas.
Curiosity’s expense, estimated at more than $1 billion, as well as the two-year delay in its launch, led to the institution of stronger requirements to maintain baseline cost and baseline schedules for future missions.
After launch by an Atlas V 541 (powered by a Russian RD-180 engine), MSL was delivered into a 103 × 201-mile (165 × 324-kilometer) orbit around Earth at a 35.5-degree inclination. At 15:33 UT, the Centaur upper stage fired to send the payload—the cruise stage and MSL—on a trajectory to Mars.
MSL used a unique entry, descent and landing (EDL) profile, designed to accommodate for the fact that the Martian atmosphere is too thin for regular parachutes and standard aerobraking, but too thick for deceleration with rockets. MSL’s relatively heavy weight— much heavier than anything ever landed on Mars—presented engineers with some serious challenges.
The EDL was entirely autonomous without ground intervention and involved four separate stages: guided entry, parachute descent, powered descent and sky crane landing. The nail-biting final moments of Curiosity’s Aug. 6, 2012, landing was called the “seven minutes of terror” by the mission team.
The guided entry within the aeroshell was helped by small attitude control jets that narrowed the landing ellipse for MSL to an area of about 12 × 4 miles (20 × 7 kilometers). Having slowed down to Mach 1.7, a supersonic parachute deployed (similar to those on Viking, Mars Pathfinder, and the Spirit and Opportunity rovers).
Curiosity’s heat shield was then discarded, and at about 1 mile (1.8 kilometers) in altitude, with velocity down to 328 feet (100 meters) per second, the actual descent stage—with Curiosity underneath it—was released from the aeroshell.
Eight variable thrust monopropellant hydrazine thrusters fired to slow the payload until Curiosity was slowly lowered from the descent stage with a 25-foot (7.6-meter) tether known as the sky crane system. The rover then gently descended to the surface at 05:17 UT Aug. 6, 2012. Just two seconds after the rover touched down, the sky crane and descent stage flew away and crashed about 710 yards (650 meters) away.
Curiosity landed at Gale Crater, a 96-mile (154-kilometer) diameter impact crater estimated to be 3.5 to 3.8 billion years old. The precise landing coordinates were 4.5895 degrees south latitude and 137.4417 degrees east longitude.
NASA named the landing site Bradbury Landing site after American writer Ray Bradbury (1920–2012), author of “The Martian Chronicles.”
On Aug. 15, 2012, Curiosity began initial instrument and mobility checks. On Aug. 19, the rover tested its laser on a rock using the chemistry and camera, or ChemCam, instrument.
Curiosity began its first drive Aug. 29, 2012, and took about two months to travel about 440 yards (400 meters) east to a location named Glenelg.
During the fall of 2012, Curiosity identified several interesting rocks that it then investigated using both the Mars hand lens imager (MAHLI) and alpha X-ray spectrometer (APXS) instruments. An area called Rocknest was also identified as an area to test out the scoop on the rover’s remote arm.
On Sept. 27, 2012, NASA announced that Curiosity had found hints of an ancient streambed, indicating that there once might have been a “vigorous flow” of water on Mars.
On Oct. 27, 2012, Curiosity conducted its first X-ray diffraction analysis of Martian soil, and Dec. 3, NASA announced the results of Curiosity’s first extensive soil analysis, which had revealed the presence of water molecules, sulfur, and chlorine. The small amounts of carbon detected could not be properly sourced and might have been from instrument contamination.
More conclusively, in March 2013, NASA announced the data from the rover, based on an investigation a rock called John Klein, suggested that Gale Crater was once suitable for microbial life. Additional analysis showed the existence of water, carbon dioxide, sulfur dioxide and hydrogen sulfide.
In terms of rover operations, on Feb. 28, 2013, the flash memory in the rover’s computer developed a problem that made the computer reboot in a loop. As a result, controllers switched to the backup computer that became operational March 19.
Curiosity drilled its second rock, called Cumberland, on May 19, 2013, creating a hole about 2.6 inches (6.6 centimeters) deep, and then delivered the material to its laboratory instruments.
In early July 2013, Curiosity left the Glenelg area and began a long trek to the mission’s main destination, Mount Sharp. A 41-yard drive on July 17 meant that Curiosity had now traveled a total distance of 0.62 miles (1 kilometer) since it landed.
As Curiosity continued toward Mount Sharp, NASA announced additional findings. On Sept. 19, 2013, scientists revealed that samples of the atmosphere Curiosity had taken six times from October to June 2012, confirmed that the Martian environment lacks methane, suggesting that there is little chance that there might be methanogenic microbial activity on Mars at this time.
On Nov. 7, the rover abruptly went into safe mode, apparently due to a software error, but controllers revived the vehicle within three days to resume surface operations. Later, on Nov. 17, there was a spurious voltage problem that suspended work for a few days.
By Dec. 5, the rover’s ChemCam laser instrument had been used for more than 100,000 shots fired at more than 420 different rock or soil targets.
Through the next few months, Curiosity returned many spectacular images, including Earth in the Martian night sky. One image returned in April 2014 showed dwarf planet Ceres and the giant asteroid Vesta.
In May 2014, Curiosity drilled into a sandstone slab rock called “Windjana,” this time at a waypoint along the route to Mount Sharp.
Curiosity passed its two-year mark on Mars on Aug. 5, 2014, having already far exceeded its original objectives. In August 2014, Curiosity was about to make its fourth drilling experiment but mission planners decided not to at the last minute because the rock, Bonanza King, was not stable enough.
On Sept. 11, 2014, Curiosity arrived at the slopes of Mount Sharp (or Aeolis Mons), now about 4.3 miles (6.9 kilometers) away from its landing point. In less than two weeks, on Sept. 24, 2014, the rover’s hammering drill was used to drill about 2.6 inches (6.7 centimeters) into a basal-layer outcrop on Mount Sharp and then collected the first powdered rock sample from its ultimate target.
Perhaps the most striking announcement of the mission was made Dec. 16, 2014, when NASA scientists announced that Curiosity had definitively identified the first instance of organic molecules on Mars. These were found in a drilled sample of the Sheepbed mudstone in Gale Crater. While these could be from organisms, it is more likely that the substance is from dust and meteorites that have landed on the planet. At the same time, new data showed that there was a recent tenfold spike and then decrease in the abundance of methane—still very tiny—in the Martian atmosphere.
Curiosity was visible in a photograph taken Dec. 13, 2014, by the HiRISE camera on the Mars Reconnaissance Orbiter (MRO). The image clearly showed the rover as it was examining part of the basal layer of Mount Sharp inside Gale Crater. A later image, from April 8, 2015, also showed Curiosity very clearly on the lower slope of Mount Sharp.
In late January 2015, Curiosity used a new, low-percussion-level drilling technique to collect sample powder from a rock target called Mojave 2. Preliminary results (based on analysis by the chemistry and mineralogy X-ray diffraction and X-ray fluorescence instrument, or CheMin instrument) suggested more acidic qualities in the form of jarosite than previous drilled samples.
On Feb. 24, Curiosity used its drill for the sixth time, this time to collect sample powder from inside a rock named Telegraph Peak that was resting on the upper portion of Pahrump Hills (also the site for the two previous drilling experiments).
Three days later, Curiosity experienced a so-called “fault-protection action” that stopped the robot from transferring sample material between devices because of an irregularity in the electric current. After a series of tests running through early March, mission planners finally directed the robotic arm to resume its work March 11 and to have it deliver a sample to the CheMin analytic instrument.
Later in March, scientists published results (in the Proceedings of the National Academy of Science) from the sample analysis by the Mars instrument suite (SAM) that indicated for the first time the existence of nitrogen on the surface of Mars released during the heating of Martian sediments. The nitrogen, which NASA called “biologically useful” was in the form of nitric oxide, perhaps released from the breakdown of nitrates. The discovery added more weight to the argument that ancient Mars once might have been “habitable for life.”
On April 16, Curiosity passed the 6.2-mile (10-kilometer) mark on its travels as it moved through a series of shallow valleys between Pahrump Hills and Logan Pass, its next science destination.
Curiosity resumed full operations after a period of limited activity for most of June when Mars passed nearly behind the Sun, relative to Earth.
In late July, the rover found unusual bedrock in a target named Elk, one with unexpectedly high levels of silica, which suggests conditions suitable for preserving ancient organic material.
On Aug. 12, 2015, Curiosity finally finished its work at Marias Pass, where it had been since May, and where it had drilled a rock target named Buckskin and found rocks with high silica and hydrogen content. It then headed southwest up Mount Sharp. (Much later in June 2016, scientists published results from an investigation of Buckskin noting that the silica mineral in question was tridymite, a material generally linked to silicic volcanism.)
Continuing its studies at Mount Sharp, on Sept. 29, 2015, Curiosity drilled its eighth hole (and fifth at Mount Sharp), one that was about 2.6 inches (65-millimeters) deep in a rock known as Big Sky as part of an experiment to analyze Martian rocks in both the CheMin and SAM instrument suites.
New results from Curiosity, published in October 2015, confirmed that billions of years ago there were water lakes on Mars. Scientists determined that water helped deposit sediment into Gale Crater, and the sediment was deposited as layers that formed the foundation for Mount Sharp, the mountain in the middle of Gale.
In December 2015, Curiosity began close examination (and returned spectacular images) of dark sand dunes up to two stories tall, located at Bagnold Dunes, a band along the northwestern side of Mount Sharp. Through the subsequent few weeks, the rover took several samples from the Samib Dune that were sorted by grain size for closer studies.
Moving on from the dunes in early March 2016, Curiosity climbed onto the Naukluft Plateau on the lower side of Mount Sharp, ending up in a stretch of extremely rugged and difficult-to-navigate terrain, with bedrock shaped by long periods of wind erosion into ridges and knobs. Here, the rover continued to take drill samples (its 10th and 11th).
On July 2, 2016, Curiosity suddenly entered into safe standby mode, but controllers were able to return it to normal operations a week later. The cause of the original switch to safe mode was a software mismatch in a particular mode, involving writing images from some cameras’ memories into files on the rover’s main computer.
Among the many thousands of images returned by Curiosity, some of the most spectacular were those of the Murray Buttes region of lower Mount Sharp. Color images showed beautiful vistas not unlike “a bit of the American desert southwest,” according to Curiosity Project Scientist Ashwin Vasavada.
Curiosity began a second two-year extended mission on Oct. 1, 2016, continuing its explorations of lower Mount Sharp. At that point, the rover had returned more than 180,000 images to Earth. NASA declared that the mission “has already achieved its main goal of determining whether the landing region ever offered environmental conditions that would have been favorable for microbial life.”
Engineers halted the use of the rover’s drill soon after while taking what would have been the seventh drill sample of the year. On Dec. 1, the Curiosity team discovered that the rover had not completed the commands for drilling. Apparently, the rover had detected a fault in the “drill feed mechanism” which was supposed to extend the drill to touch the rock target.
This problem remained unresolved until May 2018 when a new method of “percussive” drilling finally opened the path to further use of the instrument. Despite the problem with the drill, Curiosity was once again investigating active sand dunes (the so-called Bagnold Dunes).
As of Feb. 23, 2017, Curiosity had driven 9.7 miles (15.63 kilometers) since landing. By this time, it was clear to NASA engineers that the zigzag treads on Curiosity’s wheels were suffering damage, jeopardizing the wheels’ ability to carry the weight of the rover. Damage to only three treads (or “grousers”) would indicate that the wheel had reached 60% of its lifetime.
In March 2017, JPL controllers uploaded software for traction control that helped the rover adjust wheel speed depending on the rocks it is climbing. The traction control algorithm uses real-time data to vary the wheel speed, thus reducing pressure from the rocks.
Using the new software, in July, Curiosity began a campaign to study a ridge on lower Mount Sharp, informally named Vera Rubin Ridge after astronomer Vera Florence Cooper Rubin (1928–2016). The ridge was thought to be rich in an iron-oxide mineral known as hematite that can form under wet conditions. Two months later, the rover began making a steep ascent toward the ridge top.
On Oct. 17, 2017, for the first time in 10 months, the rover cautiously touched its sampler drill to a surface rock. While it was still several months away from resuming full-scale drilling operations on the Martian surface, this and subsequent tests allowed ground controllers to test techniques, including using the motion of the robotic arm directly to advance the extended bit into the rock, thus working around the mechanical problem that had suspended drill work.
NASA has made significant attempts to involve the public in the Curiosity mission. On the third anniversary of landing on Mars, in August 2015, the agency made available two online tools for public engagement. Mars Trek was a free web-based application that provides high-quality visualizations of the planet derived from 50 years of NASA exploration of Mars, while Experience Curiosity was a platform to allow viewers to experience in 3D, movement along the surface of Mars based on data from both Curiosity and MRO. NASA also released a social media game, Mars Rover, for use on mobile devices where users can drive a rover through Martian terrain while earning points.
In April 2019, scientists working with Curiosity announced the spacecraft had explored a region called "the clay-bearing unit" and tasted its first sample from this part of Mount Sharp. Curiosity drilled a piece of bedrock nicknamed Aberlady on April 6, 2019, and delivered the sample to its internal mineralogy lab.
The rover's drill chewed easily through the rock, unlike some of the tougher targets it faced nearby on Vera Rubin Ridge. It was so soft, in fact, that the drill didn't need to use its percussive technique, which is helpful for snagging samples from hard rock. This was the mission's first sample obtained using only the rotation of the drill bit.
"Curiosity has been on the road for nearly seven years," said Curiosity Project Manager Jim Erickson of NASA's Jet Propulsion Laboratory in Pasadena, California. "Finally drilling at the clay-bearing unit is a major milestone in our journey up Mount Sharp."
- NASA’s Mars Exploration Program
- Mars Science Laboratory Curiosity Mission
- National Space Science Data Center Master Catalog: Mars Science Laboratory
Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.