Study determines original orientation of rocks drilled by Mars' Perseverance Astrobiology rover

As it orbits an ancient lakeshore on Mars, NASA's Perseverance rover is assembling a one-of-a-kind rock collection. The car-sized explorer systematically drills into the Red Planet's surface, pulling out cores of bedrock it stores in sturdy titanium tubes. Scientists hope to one day return the tubes to Earth and examine their contents for traces of embedded microbial life.

Since touching down on the Martian surface in 2021, the rover has filled 20 of its 43 tubes with cores of bedrock. Now, MIT geologists have remotely determined an important property of the rocks collected to date that will help scientists answer key questions about the planet's past.

In a study published today in the journal Earth and Space Science, the MIT team reports that they determined the original orientation of most of the rock samples collected by the rover to date. By using the rover's own engineering data, such as the vehicle's position and its training, scientists can estimate the orientation of each rock sample before it is drilled from Mars.

Vision of the Perseverance Drill at Sol 371. A left mastcam-Z image of the drill with the coring bit (gold, ribbed cylinder at center) and two adjacent stabilizers (extensible gray posts with bent ends) is shown. The orientation of the drill reference frame (Dx, Dy, Dz) is shown by the white arrows, with Dˆx pointing outward along the drill shaft, Dˆy pointing perpendicular to the plane of the two stabilizers toward the planetary instrument for X-ray lithochemistry (PIXL) instrument (white box at upper left), and Dˆz along the axis of the stabilizers. axis indicates. Image ZL0_0371_0699887107_744EBY_N0110108ZCAM05070_0340LMJ02.

The results mark the first time scientists have examined rock samples from another planet. The team's method could be applied to future samples the rover collects as it expands its exploration of the ancient basin. By piecing together the orientations of many rocks from different locations, scientists can give clues to the conditions on Mars where the rocks first formed.

„There are many scientific questions in knowing the orientation of the samples we bring back from Mars,” says Elias Mansbach, a graduate student in MIT's Department of Earth, Atmospheric and Planetary Sciences.

„The orientation of the rocks can tell you about any magnetic field that existed on the planet,” says Benjamin Weiss, professor of planetary science at MIT. „You can also study how water and lava flowed on this planet, ancient wind direction and tectonic processes, what was uplifted and what sank. So, looking at the bottom of another planet is a dream because it's going to open up a lot of scientific research.

Weiss and Mansbach are co-authors Tanja Bozak and Jennifer Fentress at MIT, and have collaborators at several institutions, including the Jet Propulsion Laboratory at Caltech.

Deep change

The Perseverance rover, nicknamed „Percy,” is exploring the floor of Jezero Crater, a large impact crater lined with igneous rocks that may have been deposited from past volcanic eruptions and sedimentary rocks and long-dried rocks. Rivers fed into the basin.

„Mars was once hot and wet, and it's possible that life once existed there,” Weiss says. „It's colder and drier now, and something deeper must have happened on the planet.”

Many scientists, including Weiss, suspect that Mars, like Earth, once had a magnetic field that shielded the planet from the Sun's solar wind. Conditions then may have been favorable for water and life, at least for a time.

„Once that magnetic field disappeared, the Sun's solar wind — this plasma that boils off the Sun and moves faster than the speed of sound — hit the Martian atmosphere and removed it over billions of years,” Weiss says. „We want to know what happened and why.”

Rocks below the Martian surface may hold a record of the planet's ancient magnetic field. When rocks first form on a planet's surface, the orientation of their magnetic minerals is set by the surrounding magnetic field. The orientation of the rocks helps us trace back the direction and intensity of the planet's magnetic field and how it changed over time.

As the Perseverance rover collected samples of subsurface soil and weathered rocks as part of its mission, Weiss and Mansback, who are members of the rover's science team, looked for ways to determine the original orientation of the rover's bedrock. The models are the first step in reconstructing the magnetic history of Mars.

„It was an exciting opportunity, but initially there was no mission requirement to divert the rock,” notes Mansbach.

Geographic and site coordinate systems for the Persistence rover. Image of the Jezero Crater showing the High Resolution Imaging Science Experiment (HiRISE) rover's first 960 Sols journey on Mars. The white dots indicate positions where the rover was positioned at different times (this usually occurs at the end of a drive, but sometimes during mid-drive imaging). The rover's position on Sol 960 is indicated by the rover icon and Olivia e. Butler's Landing site is marked with a white star. The orientation of the Mars geologic frame is shown in the lower left, with Gˆx pointing north (N) of Mars and Gˆy pointing east (E) and Gˆz pointing down (D). Three example site frames and corresponding soles are indicated for Site Table 15 (pink), Site Table 19 (blue), Site Table 34 (green), and Site Table 44 (tan). The axes of each site frame are oriented within 1° of the equivalent axes in the geographic frame.

Roll with it

Over the course of several months, Mansback and Weiss met with NASA engineers to come up with a plan for how to estimate the original orientation of each rock sample before it was drilled out of the ground. A problem like predicting which direction a small circle of sheet cake is facing before twisting a round cookie cutter to scoop out a slice. Similarly, to sample bedrock, Perseverance corkscrews a tubular drill at a vertical angle to the ground, then pulls the drill straight out, including any rock it penetrates.

The team realized that to estimate the rock's orientation before it was drilled from the ground, it needed to measure three angles of the boat: pitch, yaw and roll. Hathe is the inclination of the model, while azimuth is the absolute direction the model is relative to true north. Roll indicates how much a model must turn before it returns to its original position.

Talking with engineers at NASA, the MIT geologists found that the three angles they needed corresponded to measurements the rover would take automatically during its normal operation. They realized that they could use the rover's measurements of the drill's orientation to estimate the height and azimuth of a sample, since they could assume the drill's tilt was parallel to any sample it was extracting.

To estimate the sample's roll, the team used one of the rover's internal cameras, which takes an image of the surface the drill is about to sample. They reasoned that any unique features in the surface image could be used to determine how much the sample would need to twist to return to its original orientation.

In cases where there were no distinctive features on the surface, the team used the rover's internal laser to make a mark on the rock in the shape of the letter „L” before drilling into a sample – a joke that was referred to. Time as the first graffiti on another planet.

By combining all of the rover's positioning, orientation and imaging data, the team estimated the original orientations of the 20 Martian rock samples collected so far, with an accuracy comparable to the orientation of rocks on Earth.

„We know the directions to an uncertainty of 2.7 degrees, which is better than what we can do with rocks on Earth,” Mansbaugh says. „We are now working with engineers to automate this orientation process so that it can be done with other models in the future.”

„The next phase is going to be really exciting,” Weiss says. „The rover will drive out of the crater to get the oldest known rocks on Mars, and it's an incredible opportunity to dissect these rocks and uncover a lot of these ancient processes.”

This research was supported in part by NASA and the Mars 2020 Participating Scientist Program.

Bedrock samples drilled by the Perseverance rover on MarsEarth and Space Sciences (Open Source)

Examples of rocks taken by the Perseverance rover. (a) Brac workplace on pit floor. Azimuth ∼60° clockwise from North is the center of view. The locations where the salat and cullets cores were later drilled are noted. Mast Camera Zoom (Mastcam-Z) area (Bell et al., 2021) mosaic

• QZCAM_SOL0255_0265_ZCAM08278_ZCAM08283_L0_Z34_BRAC_WORKSPACE_E01. (b) Amalik workplace on fan face. The locations where Mageik and Shuyak cores were later drilled are noted. Center of view at an azimuth of ∼190° clockwise from north. Mastcam-Z mosaic area

• QZCAM_SOL0569_ZCAM08590_L0_Z110_RASPBERRY_ISLAND_AMALIK_WORKSPACE_E01. (c) Berea site on upper fan. The location where the Melin core is then drilled is noted. Azimuth ∼330° clockwise from north is the center of view. Mastcam-Z mosaic area

• QZCAM_SOL0736SOL0739_ZCAM08745ZCAM08750_L0R0_Z110_TENBY_WORKSPACE_PDI_EXTENSION_E01. (d) Hans Amundsen memorial site on crater rim. The location where the Pelican Point core was later drilled is indicated. Azimuth ∼270° clockwise from North is the center of view.

• QZCAM_SOL0911_SOL0912_SOL0913_SOL0914_SOL0916_ZCAM08918_ZCAM08919_ZCAM08920_ZCAM08921_ZCAM08922_ZCAM0912_SOL0923_1_ZCAM08922_ZCAM08922_ZCAM08920_ZCAM08921_ZCAM08922_ZCAM08922_ZCAM08922_ZCAM08922_ZCAM08922_ZCAM08922_ZCAM08922_ZCAM08922_ZCAM08922_ZCAM08922_ZCAM08920 Complete Mastcam-Z mosaic images for these images are provided in S1–S4.

Astrophysics