A cosmic one-two punch shaped the ancient landscape of Mars
Deep within Jezero Crater, NASA’s Perseverance rover has uncovered a 245-foot-thick stack of rock that survived billions of years. This geological archive reveals a violent history of asteroid impacts and river systems that Earth's own plate tectonics would have long ago erased.
The Perseverance rover, having completed 1,000 Martian days of exploration, is currently investigating the history of a river delta in Jezero Crater [S1:p1]. This region contains layers of rock that record different eras of Martian history, including a period approximately 3.5 billion years ago when a river carved a canyon through the crater rim, depositing sand and rocks to form a delta [S2:p5]. While Earth's early geological records are often destroyed by plate tectonics, Mars' lack of crust recycling allows this ancient record to remain intact [S3:p4].
Recent findings published in the Journal of Geophysical Research: Planets highlight the 'Broom Point member,' a sequence of layered bedrock on the crater rim that is likely more than 3.9 billion years old [S3:p2]. This 75-meter-thick stack was built by repeated asteroid impacts [S3:p1, S3:p2]. Scientists identified six distinct rock types, including breccias—rocks made of angular fragments—and fine-grained rock dust [S3:p4]. The presence of abundant tiny, dark, glassy beads suggests these impacts were the primary architects of the landscape, rather than volcanic activity [S3:p5].
The landscape's complex structure suggests a massive cosmic sequence. Researchers suspect a 'one-two punch' shaped the area: first, a colossal asteroid created the 1,200-mile-wide Isidis Basin, which tilted the once-flat rock layers [S3:p7]. Later, a second impact formed the 28-mile-wide Jezero Crater [S3:p7]. Some layers in the Broom Point sequence tilt at angles exceeding 80 degrees, which is too steep to have been caused by the impact that formed the crater itself [S3:p7].
Source: Perseverance Rover Zooms in on Ancient Mars River
