A Martian rock with unusual vertical stripes around Jezero Crater, dubbed "Castle Freya," has scientists excited as it could reveal more about the history of the red planet.
NASA's Perseverance Mars rover discovered the rock and took a photo on September 13, 2024.
“Castle Freya” looks quite different from rocks seen on Mars. However, Perseverance cannot stay in the “Castle Freya” area for too long on its journey to the interior of Jezero Crater. NASA’s Mars rover has been exploring the area since landing on Mars in February 2021.
Multispectral observations from Mastcam-Z — the instrument that serves as Perseverance's primary "eyes" — showed that "Castle Freya" is only about 20cm wide. These images provided important clues about the rock's origin.
"Information about the chemical composition of this rock is limited, but initial observations suggest that metamorphic and/or igneous processes may have produced the stripes on this rock," Athanasios Klidaras, a doctoral student in planetary science at Purdue University, said in an article on NASA's Science website.
While a volcanic or metamorphic origin (a rock changing into a different type, usually under extreme heat and/or pressure) could explain the stripes, it doesn't explain how "Castle Freya" ended up where it was found by Perseverance. The rock stands out, distinct from the other pebbles and rocks in the area. It's possible that the rock rolled down from a higher ledge on the mountainside.
"This possibility excites us and we hope that as we continue to climb, Perseverance will encounter that rock outcrop so we can collect more details," said Mr. Klidaras.
In addition to "Freya Castle", in May 2024, the Mars rover Perseverance passed through the Washburn Mountain rock field. Most of the Martian rocks here are dark in color, typical of many similar rocks found on Mars, but there is one rock in the middle of this field that is bright, has a mottled texture, and is about 45cm x 35cm in size, called Atoko Point.
Measurements by NASA's Mars Reconnaissance Orbiter found that Atoko Point has pyroxene and feldspar compositions commonly found in volcanic and metamorphic rocks on Earth. Atoko Point may also have originated from other locations farther down the slopes of Jezero Crater.
The Martian rock discoveries are part of Perseverance's fourth science campaign, which focuses on searching for evidence of carbonate and olivine deposits in the 45km-wide Jezero Crater.
Carbonate rocks typically form when Mars is warmer and wetter. However, very few carbonate rocks have been discovered during exploration of the Red Planet to date. Olivine is the more common mineral on Mars and is associated with water on the Martian surface.
