Courtesy of Megan Barrington

The Mastcam-Z instrument in a clean laboratory during calibration processes.

August 10, 2020

The Red Planet Gets a Little Redder: Cornellians Work on Instruments for Mars 2020 Perseverance Rover

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On July 30, the Mars 2020 Perseverance Rover blasted off for its months-long journey to Earth’s rust-colored neighbor. On a mission to seek out microbial life on Mars, the rover is armed to the teeth with scientific instruments that can analyze the planet’s ancient climate and geology.

Cornell researchers were involved in the research, development and calibration of two of these instruments specifically designed to find traces of life on Mars: Mastcam-Z, and a subsurface radar called RIMFAX.

Experts are fairly certain that life does not currently exist on the planet. However, Megan Barrington, a Ph.D. student in the earth and atmospheric sciences department, said that the Jezero Crater landing site could have potentially harbored life within the past several billion years.

The crater, which once hosted an ancient lake filled with water, has specific key features that support this hypothesis, such as highly preserved clay deposits that could store signatures of past life. Perseverance will seek out these signatures once it lands on Feb. 18, 2021.

Barrington, a fieldwork scientist, documentarian and camera technician for experiments relating to Mastcam-Z, described the instrument as the “eyes of the rover.” The camera is extremely important for the mission, as it provides panoramic color images of the landing site and more intricate data on geology and mineral composition. Barrington further explained that the instrument’s zoom capabilities make it the first of its kind to land on Mars.

Cornellians from the astronomy and earth and atmospheric sciences departments were responsible for calibrating the Mastcam-Z cameras — a feat in and of itself.

“Mastcam-Z, our instrument, required a lot of technical calibration for us to know exactly what we’ll be looking at when an image comes back to us from the surface of Mars,” Barrington said. “In order to calibrate these cameras, we’ve spent multiple weeks of many 12 to 14 hour days, with teams the size of several hundred people, to quantify all of the parameters of our camera.”

One essential aspect of calibration was the positioning of the camera’s filters. Mastcam-Z can perceive wavelengths between 400 and 1000 nm on the electromagnetic spectrum, with each filter allowing in a smaller range of wavelengths, according to Barrington.

Calibration allows for the cameras to accurately and precisely determine the chemical composition of rocks in the Jezero Crater by collecting data on the distinct spectrum of wavelengths associated with the minerals of each rock.

The calibration of Mastcam-Z had to take place in a “clean room,” an environment free of biological contaminants to protect the delicate instrumentation during the camera experiments.

Barrington said she was thrilled to be a part of this clean room calibration process.

“Knowing that you get to be so close to this instrument that is going to change the geologic knowledge of Mars — that’s amazing to me,” Barrington said. “So that was a real treat, and it’s something that most members of the team don’t get to do.”

Barrington also participated in pre-landing training missions, which involved traveling to sites on Earth that have a mineralogy and geologic history similar to Jezero Crater. During these mock missions, Barrington and hundreds of other science team members from universities across the nation conducted experimentation using instruments that behaved like those of the actual rover.

One of these instruments Barrington worked with was the Mastcam-Z Analog Spectral Imager, developed by Cornell astronomy graduate student Christian Tate.

“[I’ve been] learning about the strengths and weaknesses of our camera…and any potential issues we might run into on the way so that we can fully understand what to expect when we start to use Mastcam-Z at Jezero Crater,” Barrington said. “No one wants to be surprised by anything on the first day that we land — we want to know as much ahead of time as possible.”

Besides Mastcam-Z, a substantial team of scientists scattered across the globe worked on another one of Perseverance’s instruments called RIMFAX, or Radar Imager for Mars’ Subsurface Experiment. One of these scientists is Cornell principal researcher Michael Mellon.

Mellon said that this radar directs radio waves downward into the subsurface of Mars and captures reflections of the radio waves as they bounce off of the underground layers back toward the surface.

These reflections can occur every time the radio wave encounters a transition in the subsurface layers, such as a change in density between soil and rock, or a change in material between rock minerals and water ice.

According to Mellon, RIMFAX will send out pulses of radio waves for every four inches the rover moves as the Perseverance traverses the terrain of Jezero Crater.

The instrument will also measure the time interval between the initial pulse of radio waves and the returned reflection, which can help scientists determine the stratigraphy at the landing site — a two-dimensional profile of rock layers beneath the surface.

“We’re going to be able to probe into those sediments [of Jezero Crater] and look for those layered structures in the subsurface, and so we can kind of help paint a picture of what the geologic history of the area was,” Mellon said.

Understanding the geologic history of Mars is crucial to determining whether the planet was habitable for early life — a question scientists have been trying to answer for decades.

“The history of the climate, the history of geology and the potential for life are all tied together. It’s often cited that there’s a common theme between them, which is water,” Mellon said. “Water leaves a signature on the geologic record, and water is intimately tied to the climate and water is the necessary ingredient for life.”

Mellon specifically researched the structure of soil on Mars, as well as the relationship between the geologic history of water ice and climate. Mellon’s research helped define important questions, such as how deep the radar should penetrate and what it should be looking for, informing the engineering requirements of the instrument.

Because of this, RIMFAX will be able to make useful measurements of subsurface structures that could indicate the presence of ice in the past, along with other key parameters.

In preparation for Perseverance’s landing, both Mellon and Barrington will be training for, practicing and refining the procedures involved in the post-landing operation of their respective instruments. This will require the collaboration of the entire science teams behind each instrument, allowing for smoother coordination once operation of the rover actually begins in six months.

Despite the long road ahead of her, Barrington said it was a gratifying experience to work on Perseverance.

“It’s been a total dream experience,” Barrington said. “Coming here and participating in the project for Mastcam Z and the Mars 2020 [mission] has been so very exciting and fulfilling, and I’ve never been prouder of the work that I do.”