As the saying goes, everything that has a beginning has an end. Many students in my lab have had the opportunity to work on the Curiosity mission over the last ten years and it has been one of the great joys of my career to see those students grow into capable and confident colleagues trusted by their peers the world over who work with them on the mission. But, inevitably, students complete their degrees or move on to other projects and opportunities. For Charissa Campbell, a PhD student who has been working on the mission since 2016 she has an opportunity to lead the science case for an instrument called MAPLE that could contribute to Environmental Science in a future planetary mission.
(Animation Above: the sun sets at Gale Crater on Sol 312 of the mission)
By Charissa Campbell
Over the past 5 years, I’ve been a part of the Mars Science Laboratory (MSL, Curiosity) team, specifically the Environmental working group (ENV). The ENV team is responsible for managing any environmental observations which includes any cloud or dust devil imaging. During my time with the group I got the opportunity to help plan several sols (Martian day) of operations. This includes advocating for different ENV observations that are used to characterize the environment around Curiosity’s location, Gale Crater.
Our research group helps maintain different ENV observations that use the Navigation Cameras (Navcams) to observe atmospheric aerosols. This includes the Zenith Movie (ZM, an eight frame movie observing movement directly above the rover), Supra-horizon Movie (SHM, an eight frame movie looking above the horizon), Line of Sight (LOS, a single image capturing the crater rim), Phase Function Sky Survey (PFSS, 9 three frame movies observing aerosols at a variety of pointings) and Cloud Altitude Observation (CAO, 2 eight frame movies intending to capture cloud and shadow motion). The first three (ZM, SHM, LOS) have been a part of the mission for several Mars Years (MYs) and are great for monitoring cloud and dust over the course of a MY. The PFSS and CAO are on the newer side and are only performed in the cloudy season. The most recent cloudy season just finished and now we are preparing for the dust season which brings increased dust and dust-devils in the crater.
When I first started on the mission, I helped maintain the cadence of the ZM and SHM. This includes advocating their cadence (every 2-3 sols) and keeping an eye out for any aerosol activity. The cloudy season on Mars is very consistent year to year so it is relatively easy to predict when we’d expect to see more activity. Coming up to my first cloudy season, I found a pair of early morning movies that captured wispy clouds like Mares’ Tails seen here on Earth (shown below). The uniqueness and beauty of these clouds earned a press release (https://mars.nasa.gov/resources/8866/clouds-sailing-overhead-on-mars-enhanced/?site=msl). Since I was still fresh on the mission, I was excited and anxious for the opportunity. It received plenty of press and I enjoyed reading the various comments left by the public.
Over the next few years I continued to advocate for ENV observations but I was also given the opportunity to help develop a new observation. On sol 1787 a Dust-Devil Movie (DDM) was aimed at Mt. Sharp (Aeolis Mons) and instead of capturing dust-devils, it observed shadows moving across the mountain. This was caused by clouds moving overhead which was confirmed by the ZM that followed. A DDM pointed at Mt. Sharp posed a unique opportunity to measure the direct velocity and altitude of the overhead clouds by determining how fast the shadows move with respect to the mountain. Digital Terrain Models (DTMs) have been created for Mars which provide an x, y, z coordinate for every point in Gale Crater. By noting where on the mountain the shadow starts and ends between the first and last frames, a velocity can be calculated. When a paired ZM is used to calculate the angular spacing and velocity of the clouds above, we can get the velocity and altitude of the clouds. Typically, this parameter is found using a lidar which was demonstrated by the Phoenix lander (https://www.nasa.gov/mission_pages/phoenix/images/press/Lidar_Fall_Streaks_SD_001.html). However, Curiosity isn’t equipped with a lidar so we must use alternative approaches to calculate altitude.
Taking what we learned about the DDM and ZM combination, we went ahead and created the CAO. Within this parent observation is the Cloud Shadow Movie (CSM) and ZM. The CSM would be the DDM but optimized to bring out shadows. This includes increasing the frame size for more mountain coverage. This frame size was also applied to the ZM. Once the CAO was optimized , it was tested on Curiosity before becoming an official observation that the ENV team can plan. As of today, we have officially completed 3 MY worth of CAO data.
Analyzing the most recent set showed a unique pair of shadow and clouds that were not seen before in a CAO. Shown below, both movies show turbulent clouds with large shadows that pass over the rover before going up the mountain. I decided to showcase this set at the most recent Curiosity team meeting where I showed my cloud altitude results. The movies seemed to be a hit that they became a press release (https://mars.nasa.gov/resources/26557/curiosity-captures-drifting-clouds-on-dec-12-2021/?site=msl). It made me extremely happy to have another set of movies released by JPL. I will be leaving the Curiosity team in the next few months to focus on my other PhD projects, so it is bittersweet to start and end my time on the mission with a press release.
It’s been a great honour to work with Curiosity data and especially help develop an observation that will continue to be captured in future cloud seasons. I want to thank the Curiosity team and all the current and past PVL members that have helped me. Good luck Curiosity! I hope you have many more cloudy seasons on the horizon.
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