Since touching down at Octavia E. Butler Landing on the surface of Mars in February 2021, the Mars 2020 Perseverance rover has had an exciting and productive first nine months in Jezero crater, the 50-kilometer-wide impact crater it now calls home.
After an initial period of instrument and engineering checkouts, including a series of successful flights by the Ingenuity helicopter that accompanied Perseverance to Mars, the rover began a focused campaign to explore the rocks of the crater floor, including the successful acquisition of its first rock samples. Meanwhile, long-distance observations of ancient delta deposits preserved within the crater have provided the first detailed insights into the evolution of the Jezero crater lake system.
The Perseverance rover is NASA’s newest flagship mission to Mars, and the first step of a multi-mission campaign to return samples from Mars back to Earth.
The Mars 2020 mission has four science objectives:
- Characterize the geology and habitability of the rover’s landing site
- Seek signs of ancient life in rocks and soils analyzed by the rover
- Collect a cache of scientifically compelling, returnable samples
- Prepare for future human exploration of Mars.
The rover carries 43 sample tubes, including several tubes that will act as witness “blanks” throughout the mission, with the anticipated goal of collecting about 30 science samples during the surface mission.
Jezero crater was chosen as the rover’s field site because it hosts well-preserved fluvial, deltaic and possibly lacustrine deposits. This site also provides access to rocks of diverse compositions including carbonates, clays and olivine on the floor, inner margin and rim of the crater. These rocks might represent a range of ancient habitable environments in a variety of surface and subsurface and sedimentary, volcanic and impact-related settings.
Living on Mars Time
During the first three months of the mission, scientists and engineers operating Perseverance lived on “Mars time,” meaning that they lived and worked around the Mars day, which is about 40 minutes longer than an Earth day. The schedule of Earth and Mars sometimes aligns, but there were weeks-long periods of time when the Perseverance team worked through the night to keep up with the rover.
The mission’s list of “firsts” grew quickly during the early weeks: first color image of the landing site, first instrument checkouts, first movement of the robotic arm, first drive and first sounds from the surface of Mars recorded by the rover’s microphones. The rover’s next task was to drop-off the Ingenuity helicopter, which was stored under the body of the rover during launch, cruise and landing. Then came the next major first: controlled, powered flight on another planet.
After a few blade-spin tests and a flight software update, Ingenuity made history with its first flight on April 19, 2021. After five successful technology demonstration flights, Ingenuity transitioned to a new phase of its mission, aiming to prove how aerial scouts could aid future planetary exploration missions. As of this writing, Ingenuity has successfully completed 15 flights, and images taken by the helicopter have already proven helpful for rover mobility and science assessment, providing views of the surface complementary to those provided by the rover and orbiting satellites.
The Science Mission
Once the rover had accomplished its major initial checkouts, the team was eager to begin the science mission. Having landed about 2 kilometers east of the main Jezero delta deposit, the rover was well-positioned to carry out a detailed investigation of the rock units comprising the crater floor. Perseverance landed very near a major geologic contact marking the transition between distinctive olivine-bearing rocks interpreted to be older than nearby heavily-cratered rocks containing mafic minerals like pyroxene, but no clear sign of olivine as observed in orbiter spectroscopic data.
While the rover team worked to get sampling capabilities on-line, they commanded Perseverance to drive south from Octavia E. Butler Landing, acquiring images and geochemistry and mineralogy data of the crater floor rocks along the way. Perseverance also used its ground penetrating radar system, called RIMFAX, to observe structure and stratigraphy in the sub-surface, as it drove. Rover observations revealed that the crater-retaining units of the Jezero crater floor are comprised of variably massive and layered mafic rocks exposed in flat polygons and high-standing, erosion-resistant outcrops.
Perseverance used its abrading capabilities for the first time at an outcrop called “Roubion” where subsequent imaging and compositional analyses showed the rock to be comprised of relatively coarse grains of pyroxene and plagioclase, as well as salt minerals such as sodium chloride and sulfates. The presence of salt minerals suggests that the rocks experienced sustained interaction with ground water, creating a habitable environment that could have hosted ancient microbial life.
Perseverance achieved its next major mission milestone farther along the traverse at a boulder named “Rochette,” where the rover successfully collected, processed and sealed its first two rock cores. Although the team is still pouring over the data collected from Roubion and Rochette, the leading hypothesis is that these rocks represent ancient lava flows. If they are indeed crystalline, igneous rocks, the samples collected by Perseverance would be ideal for radiometric dating if they are returned to Earth. Most recently, Perseverance crossed the contact into olivine-bearing rocks of the crater floor, and is preparing to acquire its next pair of samples in this unit.
Although the Jezero delta deposits remains several kilometers away, long-distance imaging of the western scarp of the delta and of remnant mounds have provided a first look at the sedimentology and stratigraphy of these deposits. In a recent study published by the rover team in Science, Mangold and co-authors identified delta topset, foreset and bottomset beds in the exposed scarps of a remnant mound called “Kodiak.” This sequence was interpreted to represent the progradation of steeply-fronted Gilbert-type deltas into the ancient Jezero crater lake.
Lenses of conglomerate observed within the main delta deposit suggest a very different environment of deposition. These deposits, which contain boulders up to 1.5 meters in diameter, are interpreted to represent episodic, high-energy fluvial deposits that could have formed upstream from the delta, or they could represent a significantly younger episode of deposition, post-dating the Jezero crater lake. When coupled with observations of the Jezero delta, Perseverance’s investigation of the crater floor supports a model involving the evolution and interplay between an episodic fluvio-lacustrine system and volcanic activity in the region.
Its Ongoing Mission
Perseverance will spend the upcoming months completing its exploration of the Jezero crater floor before it begins the trek to the delta. The team is very much looking forward to this next phase of the mission at the Jezero delta, during which the rover will explore some of the most astrobiologically compelling rocks in the region. If the first nine months are any indication, there are great scientific discoveries, and likely a few surprises, in store for Perseverance and its team.
Acknowledgments: This article was written at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.