2025-02-17

Where Science Meets Art: The Mastcam-Z Calibration Target

Contributed by Katherine Winchell, 17 February 2025

In January, ASU hosted a Mastcam-Z team meeting with around 40 in-person, and several remote attendees. We took this time to collaborate with each other and provide updates on what individuals on the team have been working on in the past months or year.

Spacecraft missions traditionally have team collectibles, and in-person meetings like this one would not be complete without them! The postcards that we use for public outreach are always a huge hit amongst team members, but we wanted to provide something new for this meeting as well! So the question became, outside of the ZCAM logo and images taken by the instrument, what defines Mastcam-Z? The answer I came to is the radiometric calibration target, for our purposes in the form of a sticker.

Mounted on the body of the Perseverance rover, this metal and ceramic scientific instrument is used as a benchmark to help scientists better understand the mineralogy of rocks and soils imaged by Mastcam-Z by giving us a set of standard, well-characterized grayscale and color patches to image under roughly the same conditions as when multispectral images are taken. This comparison is useful to scientists because the amount of illumination in an image changes hour by hour and sol by sol (a sol being a Martian day) due to the angle of the Sun and the amount of dust in the atmosphere. We image the calibration target every time we take a multispectral image with Mastcam-Z so we have something to calibrate our data with, making this calibration target the most frequently imaged object of the Perseverance mission. You can read more about the technical details of the calibration target in this blog post by Kinch et. al, or this scientific paper by Merusi et. al.

The primary calibration target displays some “festooning” that was developed by the Mastcam-Z team in collaboration with The Planetary Society, which adds an artistic human element to the functional design. These elements have the goal of communicating the intent and historical context of the instrument’s mission for future generations, drawing from themes commonly found in speculative and science fiction.

The motto, “Two Worlds, One Beginning,” was laser engraved into the surface of the calibration target, meant to evoke the similar motto found on the calibration targets for Pancam on the Spirit and Opportunity rovers, “Two Worlds, One Sun.” The font, Eurostile, was chosen as a merging of science and science fiction, as it has been extensively used in science fiction films, such as Star Trek and 2001: A Space Odyssey.

Also engraved on the surface of the calibration target are seven images, or “vignettes” that are meant to be read starting at the bottom left and moving clockwise to tell the story of Earth and our place in the solar system.

The first three vignettes depict the early history of earth. The depiction of the inner planets of our solar system is shown in the approximate positions of the planets at the time of the Perseverance rover’s landing on February 18th, 2021. The DNA strand and cyanobacteria represent the first life forms on Earth. They are particularly fitting inclusions as one of the primary missions of the Perseverance rover is to seek signs of past life on Mars, and we suspect that if life ever did develop on Mars, it could have begun in a similar way.

The next three vignettes show the development of more complex life forms on Earth. First photosynthetic life is symbolized by the fern, then an Apatosaurus symbolizes the diversity of animal life, and then finally humans, whose depiction echoes that on the Voyager Golden Records.

The seventh and final vignette shows a retro stylized rocket, symbolizing Perseverance’s travel to Mars. Originally a more realistic depiction of a rocket was drafted, but it was decided that it was visually too similar to a missile, and our intentions are better portrayed by a classic science fiction rocket that was popular at the time of the dawn of the Space Age. The rocket is placed between the blue and red circular color patches that have technical use, to symbolize the journey from Earth to Mars.

Not pictured on the sticker version, but engraved on the edge of the actual calibration target is this message:

“Are we alone?  We came here to look for signs of life, and to collect samples of Mars for study on Earth.  To those who follow, we wish a safe journey and the joy of discovery.”

The remaining space on the calibration target edge is the phrase “joy of discovery” repeated in the five other most spoken languages on Earth, Mandarin, Hindi, Spanish, and Arabic. Since the edges are not fully visible to our cameras, this message is intended for future astronauts who will hopefully see the Perseverance rover as a historical landmark.

Back to Earth, and for our January team meeting – I needed some help. My graphic design skills are limited, so I reached out to a friend of mine, Ryan Miorelli, who is much more experienced in this realm to create an artistic depiction of the calibration target. I sent him many reference photos, and he created this for us! It made a great sticker, which was well received by the entire team. The sticker ended up on many laptops that have now made their way back to all corners of the world where the Mastcam-Z team resides.

You can use this file to print your own stickers if you would like! Keep in mind that due to the appendages where the calibration target attaches to the rover, the main body of the sticker will be smaller than the listed print size. For example, I purchased three inch stickers for this team meeting, and the main body of the calibration target printed as a little over two and a half inches.

Speaking of printing the calibration target, check out this blog post by Sarah Al-Ahmed detailing how to print your own 3D model of it!

I hope you take some time today to find the joy in discovery, and appreciate the intersection of STEM and art.