PERSEVERANCE AND THE RED PLANET

BY COURTNEY ANTOLIK, NATE ROGERS, WYLIE WALKER AND NATE LAFONTAINE

A new visitor landed on Mars this February: the Perseverance rover. It is accompanied by a robotic helicopter named Ingenuity and will explore Mars for the next Martian year (about 21 months on Earth). Perseverance is the fifth rover to land on Mars, following in the tracks of the Sojourner, Opportunity, Spirit and Curiosity rovers.

Perseverance is a key part of NASA’s Mars Exploration Program (MEP), a science-driven and technology-enabled study of the Mars planetary system. Why explore Mars? The Red Planet is one of the most accessible places in our solar system and has atmospheric, climatic and geologic systems similar to Earth’s. The planetary history and evolution of Mars can help answer questions on Earth about the origins of life, and the future of our home. If Mars proves to be hospitable to human life, it could one day become home to humans.

FIGURE 1: Perseverance instruments. Many of the instruments aboard Perseverance are similar to those geologists use on Earth.

Photo from NASA.

Perseverance has a busy road ahead with four main mission goals: determine whether life ever existed on Mars, characterize the climate of Mars, characterize the geology of Mars, and prepare for human exploration.

LIFE ON MARS

Water is essential for all forms of life. Previous Mars explorations have found frozen water in polar ice caps, subglacial ice and ground ice. Although there is no liquid water on Mars today, there is evidence that it once existed. Deltas and river and lake valleys are surficial evidence for ancient water flow on Mars, while hydrated minerals provide chemical evidence. A recent paper in Science suggests that the water that used to flow on Mars is now trapped in the rocks on Mars.

FIGURE 2: (a) Jezero Crater landing site. Image taken by the Mars Reconnaissance Orbiter in 2019.

Image from NASA/JPL-Caltech/MSSS/JHU-APL.

FIGURE 2: (b) River delta analogue on earth. River deltas in the Lake Ayakum Tibetan Plateau.

Photo courtesy NASA (https://earthobservatory.nasa.gov/images/50500/river-deltas-lakeayakum-tibet)

Perseverance is searching for biosignatures of life in the Martian soil and rocks. On Earth, biosignatures include carbon (or carbonate minerals) and fossils. The signs of ancient life on Mars may be quite different, but this is a good place to start. On a previous expedition, the Mars reconnaissance orbiter found evidence of clay minerals in the Jezero Crater–minerals that only form in the presence of water. Perseverance began its search for life in Jezero Crater, a 28-mile-wide crater just north of the Martian equator (Figure 2). Jezero is part of the Isidis Planitia region, a 750-mile-wide basin that formed from an ancient meteorite impact. Scientists believe that a river once flowed into Jezero crater, making it an excellent place to explore.

WATER ON MARS

Imagery of the Jezero crater appears to show an ancient lake and river system (Figure 3). The fanshaped apron of debris and meandering channel patterns are characteristic of river deposits here on Earth. NASA scientists chose the Jezero crater as the Perseverance’s landing spot for several reasons. The rocks in the crater may have preserved ancient organic molecules or other microbial life forms from the river water that flowed into the crater billions of years ago. Carbonate and clay rocks in the Jezero crater are good candidates for preservation. The rocks in Jezero can also tell scientists about the conditions outside of the crater, since rocks and minerals from other areas were likely deposited in the crater by the ancient river.

FIGURE 3: This annotated mosaic depicts a possible route the Mars 2020 Perseverance rover could take across Jezero Crater as it investigates several ancient environments that may have once been habitable. The route begins at the cliffs defining the base of a delta produced by a river as it flowed into a lake that once filled the crater. The path then traverses up and across the delta toward possible ancient shoreline deposits, and then climbs the 2,000-foot-high (610-meter-high) crater rim to explore the surrounding plains. About half of this traverse could be completed in Perseverance’s prime mission (one Mars year, or two Earth years). For reference, the prominent crater near the center of the image is about 0.6 miles (1 kilometer) across. This mosaic is composed of multiple precisely aligned images from the Context Camera on the Mars Reconnaissance Orbiter and has a resolution of 20 meet (6 meters) per pixel.

Photo from NASA/JPL-Caltech.

An alternative theory suggests that some Martian river channels were formed by meltwater underneath glacial ice sheets, instead of flowing rivers (Figure 4). Researchers from the University of British Columbia, Western University and Arizona State University compared imagery of channels and valleys on Mars to glacially carved channels on Earth. They found striking similarities between Martian river channels and the glacially carved channels in the Canadian Arctic. The theory is coupled with ancient climate data suggesting the Martian climate was too cold to support running water when the valleys and channels formed. Data collected by the Perseverance rover should provide more insight into the origin of Mars’ valleys and channels.

Figure 4: Left: Glacier-cut channels on Devon Island in the Canadian Arctic. Right: channels on Mars in the Maumee Valles region.

Photo from Cal-Tech CTX mosaic and MAXAR/Esri.

CLIMATE OF MARS

The Perseverance rover will also help scientists characterize the climate of Mars. Data from previous Mars exploration missions suggest that rivers and lakes once existed on Mars, but the planet is now dry. Understanding the climate history of Mars can give scientists insight on what the Earth’s future climate may be like, and if Mars is hospitable to human exploration.

Mars has seasons similar to Earth’s, thanks to its axial tilt of 25°. However, the seasons on Mars are twice as long as seasons on Earth, as Mars is much farther away from the sun. The Martian atmosphere is composed of CO2 and very thin–only 1% as thick as the Earth’s atmosphere (Figure 5). Like Earth, Mars has polar ice caps, although they are primarily composed of CO2 with some frozen water. Seasonal changes in the polar ice caps and movement of large amounts of dust in the atmosphere control the climate on Mars.

Meteor Crater in Northern Arizona

Source: Forbes

FIGURE 5: Meteor impacts are frequent on Mars, due to its thin atmosphere. The post-depositional impact crater “Belva” sits within the fluvial delta bordering the Perseverance landing site. Unlike Earth, preservation of impact craters is extremely common on the surface of Mars, reflecting the low erosion rates. Note the presence of bedforms within the crater, likely reflecting aeolian sedimentary processes.

Sources: Forbes and NASA.

Atmospheric temperatures on Mars vary wildly, from -243° F at the poles to 68° F at the equator. The temperature differences create high wind speeds and the dust storms that give Mars its nickname. Dust storms are especially prevalent in the southern spring and summer and can encompass the entire planet.

Data collected by Perseverance and other rovers will help scientists make detailed weather maps and understand how much dust and water vapor are in the Martian atmosphere. Just like on Earth, the Martian rock record holds clues to the planet’s climatic history.

GEOLOGY OF MARS

Mars and Earth are similar geologically. Both planets are terrestrial and have a core, mantle and crust. While the Earth’s plates are constantly moving, creating volcanoes and mid-ocean spreading centers, Mars is tectonically dead. Temperature differences between the Earth’s liquid outer core and the mantle drives convection in the mantle and plate tectonics. Although Mars is thought to have a molten core, there is no convection in the mantle, and thus, no plate tectonics. As a result, the crust of Mars is very thick compared to the Earth’s crust.

The rocks that make up the surface of Mars are basalts, similar to Earth’s oceanic crust. Although Mars is about half the size of Earth in diameter, the two planets have roughly the same dry land surface area. This is because 70% of the Earth’s surface is covered with water, while Mars has no liquid water on its surface.

Despite the tectonic differences, the surface of Mars is similar to the surface of the Earth, suggesting that similar geologic processes occurred on both planets. Both planets have volcanoes, valleys, craters, layered sedimentary rocks, channels and deltas (Figures 6-9). However, it’s still not clear how geologic forces like wind, water and volcanoes have worked together to shape the surface of Mars.

Understanding Martian geology is the key to understanding its formation and planetary evolution. The data collected by Perseverance will help scientists understand the timing and composition of Martian rocks, critical information in the search for life. Martian geology can also shed light on the origins of some of the key differences between Mars and Earth. For example, Mars does not have a convectively flowing liquid mantle and magnetic field like Earth, but magnetic materials on Mars suggest that it once did. An ancient magnetic field means Mars may have once been tectonically active like Earth, as magnetism would have affected Mars’ interior structure, temperature and composition. A magnetic field also has implications about life, as Earth’s magnetic field shields the planet from harmful cosmic rays.

FIGURE 6: An image of the Mars Perseverance Landing Site at Jezero Crater (left) shows geomorphology similar to that found on Earth, as shown in the desert of Coconino County, NE Arizona (right). The Mars image show characteristic signs of fluvial processes cutting through an escarpment and depositing in an interpreted delta front near the landing site. Off-axis of the deltaic deposits are arcuate-shaped deposits, possibly representing earlier deposition or aeolian processes acting at the base of the escarpment. These processes can be identified in the Coconino County analog, with fluvial deposits cutting through an escarpment and depositing at the toe of the escarpment. Similar arcuate deposits are observed here where aeolian processes redistribute sediment.

FIGURE 7: (a) Layered sediments in a delta on Mars (NASA)

https://www.bbc.com/news/in-pictures-56238018

FIGURE 7: (b) Layered sediments in the Mancos Shale, near Green River, UT

photo by Nate Rogers

FIGURE 8: (a) A wind-carved rock on Mars

NASA/JPL-Caltech/MSSS/ASU (https://mars.nasa.gov/resources/25642/a-wind-carved-rock/)

FIGURE 8: (b) compared to a wind-carved rock in the Altiplano region of Bolivia.

Wikipedia

FIGURE 9: The Olympus Mons shield volcano on Mars is over 21 km tall and is the tallest planetary mountain in the solar system.

NSF

WHAT’S NEXT ON MARS?

On April 8, 2021, the Ingenuity helicopter that accompanies Perseverance will take flight. Ingenuity will complete several test flights, operating autonomously and recharging its batteries with solar power. The purpose of Ingenuity is to test and develop powered flight on Mars–a tall order, given the drastic atmospheric and temperature differences between Mars and Earth. If Ingenuity proves to be successful, this could pave the way for human exploration of Mars.

Perseverance will continue exploring and collecting data on Mars for the next Martian year. Part of the rover’s duties is to collect core and soil samples and store them for the future return to Earth. The Mars Sample Return Mission, planned for 2026 or 2028, will send a Sample Retrieval Lander to Mars to collect the samples left by Perseverance. These samples will be dropped into orbit around Mars and collected by another spacecraft, the Earth Return Orbiter. If all goes according to plan, the samples will be back on Earth by 2031.

SOURCES AND FURTHER READING:

https://www.nasa.gov/press-release/nasa-ingenuity-mars-helicopter-prepares-for-first-flight

https://mars.nasa.gov/mars2020/

https://www.sciencedaily.com/releases/2021/01/210121131947.htm

https://www.nytimes.com/2021/03/19/science/ mars-water-missing.html

https://www.washingtonpost.com/news/capital-weather-gang/wp/2015/10/18/the-weather-on-mars-is-both-totally-alien-and-somewhatearth-like-all-at-once/

https://earthsky.org/space/mars-river-channels-ice-sheets-devon-island-canadian-arctic-archipelago

https://www.cbsnews.com/news/nasa-mars-landing-perseverance-rover-rock-sample-return-mission/

https://www.popsci.com/story/space/ asteroid-impacts-moon-mars/

FIGURE 10: Ingenuity helicopter on Mars.

NASA