In late April, Perseverance and Ingenuity arrived at the edge of Jezero Crater’s ancient river delta — an area of the crater that was likely once formed by flowing water, and a major focus of the Mars 2020 mission. Perseverance‘s arrival at the delta marked the beginning of the rover’s second science campaign in the crater, officially kicking off on sol 407 of the mission.
“The delta at Jezero Crater promises to be a veritable geologic feast and one of the best locations on Mars to look for signs of past microscopic life,” said Thomas Zurbuchen, the associate administrator of NASA’s Science Mission Directorate.
What’s more, as Perseverance and Ingenuity were studying Mars on the surface, Mars Odyssey and a team of researchers were solving a mystery involving invisible Martian frost and dust avalanches.
Mars 2020 begins second science campaign
A major focus of the Mars 2020 mission is to search for signs of past biological life and research the possible habitability of Mars millions and billions of years ago. To achieve these goals, Mars 2020 team members decided to land Perseverance and Ingenuity in Jezero Crater — a massive crater once thought to be filled with flowing water.
One of the likely sources of Jezero Crater’s water was a large river delta located on the western side of the crater. When determining where to land Mars 2020, the Jezero delta was a major point of interest for the teams as life forms would have likely flourished there.
After landing near the delta in February 2021 and completing the commissioning process, Perseverance and Ingenuity departed Octavia E. Butler Landing and began their first science campaign. However, this science campaign would see the robotic duo travel away from the delta rather than towards it.
A primary focus of the mission’s first science campaign was to collect, characterize, and study rocks, bedrock, and other surface features in Jezero. The two areas the first campaign was focused on were the Séítah and the Crater Floor Fractured Rough, both located south of the rover’s landing site.
As aforementioned, Perseverance‘s successful collection of surface samples was a primary focus of the first science campaign in Jezero. In total, Perseverance collected eight surface samples in the Séítah and the Crater Floor Fractured Rough areas — proving that the rover’s sample collection system worked as intended.
Perseverance collected the eighth and final sample of the first science campaign on sol 377 in March, officially bringing the campaign to a close.
With the first campaign over, the Perseverance and Ingenuity teams set their sights on the intriguing Jezero delta. However, they first needed to get there — and they wanted to get there fast.
To reach the delta as soon as possible, Perseverance teams programmed the rover to begin a daring five-kilometer dash across Jezero’s surface to reach the delta on March 14 — all the while traveling faster than any other Mars rover that preceded it. What’s more, Ingenuity periodically flew alongside Perseverance as the rover made its trek to the delta, flying some of the longest and furthest flights the little helicopter has performed on the red planet.
Ripples and ridges at the delta’s edge. Excited to start science activities at this destination we’ve had in our sights for so long. The finely layered rocks just ahead may be my next target for #SamplingMars.
— NASA’s Perseverance Mars Rover (@NASAPersevere) April 28, 2022
Perseverance finally arrived at the Jezero river delta on April 13 at the completion of its five-kilometer trek across the crater’s floor. Upon arriving at the delta, the rover snapped multiple images to survey the surrounding environment for potential surface features or formations of scientific interest.
“We’ve been eyeing the delta from a distance for more than a year while we explored the crater floor. At the end of our fast traverse, we are finally able to get close to it, obtaining images of ever-greater detail revealing where we can best explore these important rocks,” said Ken Farley, Perseverance project scientist at Caltech.
Perseverance‘s second science campaign officially started on April 18, with Perseverance exploring an area of the delta known as the “Three Forks.” Titled the “Delta Front campaign,” Perseverance teams kicked off the campaign by driving to the southwest and west to scope out the best route up the delta, which rises to around 40 meters above Jezero’s floor. After scouting out locations for a week, teams identified two locations, now dubbed “Cape Nukshak” and “Hawksbill Gap,” both of which appear to be traversable by Perseverance.
Teams ultimately decided to take the Hawksbill Gap route. During its trek up and down the delta on the Hawksbill Gap route, Perseverance will collect around eight surface samples while characterizing and researching various rocks and surface features that might give clues to the delta’s past. The samples Perseverance collects will likely be of layered sedimentary rock deposited into the delta by flowing water, wherein ancient biosignatures of past life could be present.
After Perseverance reclimbs the delta slopes following its first climb, the Delta Front campaign will come to a close and the third science campaign, titled the “Delta Top campaign,” will begin. The Delta Top campaign, as the name suggests, will see Perseverance collect samples of and research the top of the delta.
Perseverance is currently climbing the slopes of the delta and will continue to throughout the next few weeks — periodically stopping to either collect samples, take photos, or characterize and research interesting surface features in the delta. The second science campaign is set to last around half an Earth year.
Mars Odyssey solves frost mystery
Last year, NASA’s Mars Odyssey orbiter — the agency’s longest-lasting Mars mission and recent recipient of a mission extension — snapped multiple images of the Martian surface at dawn. Upon analyzing the images in visible light and using the orbiter’s heat-sensitive camera to collect additional images, scientists were quickly baffled by what they were seeing on the Martian surface.
When analyzing the images in visible light, the group of scientists were seeing a ghostly, blue-white frost layer in certain areas of the Martian surface. However, when viewing the images using the orbiter’s heat-sensitive camera, they found that the ice actually covered a much larger portion of the Martian surface than could be seen in visible light. What’s more, the scientists found that the ice layers were likely responsible for Martian dust avalanches.
The scientists already knew that the frost had formed overnight and was mostly carbon dioxide, making the ice layer essentially dry ice, as carbon dioxide ice more commonly forms on Mars’ surface than water ice. However, the part of the images that was truly baffling was why the ice could be seen in some areas and not in others.
Using Mars Odyssey’s Thermal Emission Imaging System (THEMIS), the scientists were able to uncover the mystery behind the formation of this unique dry ice frost.
When collecting the images used in the study, teams would aim THEMIS at the surface around 7:00 a.m. local Mars time, providing a unique look at the Martian surface as the Sun just began to rise over the horizon and heat the Martian atmosphere.
On Earth, surface ice and frost layers can stay frozen for minutes, hours, and sometimes full days after the Sun rises due to the density of Earth’s atmosphere and the varying climatological patterns in certain areas. However, Mars’ atmosphere is extremely thin, just one percent the density of Earth’s, so the Sun can very quickly heat the atmosphere soon after it rises over the horizon.
Due to this intense and quick warming of the Martian atmosphere, most dry ice or frost layers on the Martian surface will vaporize into the atmosphere in just minutes rather than melt into the surface over several hours.
One of the scientists, Lucas Lange, first noticed a cold signature associated with frost that was not visible in visible light. Interestingly, this cold signature was being detected just tens of microns below the Martian surface, which is less than the width of a human hair.
“Our first thought was ice could be buried there. Dry ice is plentiful near Mars’ poles, but we were looking closer to the equator of the planet, where it’s generally too warm for dry ice frost to form,” said Lange.
Ultimately, the scientists determined that the invisible frost was known as “dirty frost” — a dry ice form mixed with fine grains of Martian dust. These fine dust grains obscure the frost in visible light but not in infrared and heat-sensitive images — which explains why the scientists were seeing the frost in infrared images but not in visible light images.
What’s more, the vaporization of this ice could be responsible for dust avalanches on Mars, Piqueux et al. explain in their report.
When the frost layers vaporize on the slopes of mountains or large sand dunes and hills, they are thought to cause the formation of dust avalanches down the side of said mountains, dunes, and hills — creating long, dark brown streaks on the Martian surface. Unlike recurring slope lineae, which are very similar to the dust avalanches and better documented, these dust avalanches occur very quickly over the course of a few hours, instead of weeks.
Upon mapping the location of these dark streaks caused by avalanches, Piqueux et al. found that the avalanches tend to occur in areas where the morning dry ice frost is located. Specifically, the scientists believe that the vaporization of the frost creates just enough pressure to loosen a few Martian dust grains, creating an avalanche.
“Every time we send a mission to Mars, we discover exotic new processes. We don’t have anything exactly like a slope streak on Earth. You have to think beyond your experiences on Earth to understand Mars,” said Chris Edwards of Northern Arizona University in Flagstaff and one of the paper’s co-authors.
Piqueux et al.’s research and results were published in the Journal of Geophysical Research: Planets last month.
Lead image: Artist’s illustration of Mars Odyssey orbiting Mars (left), Perseverance snaps a selfie during its first science campaign in Jezero Crater (right). (Credit: NASA/JPL (left), NASA/JPL-Caltech (right))
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