Ancient River Delta Uncovered Deep Beneath Martian Surface
NASA’s Perseverance rover has unearthed compelling evidence of an ancient river delta buried deep beneath the surface of Mars, offering some of the most profound insights yet into the planet’s watery past. The discovery, made using ground-penetrating radar, paints a vivid picture of a once dynamic environment on Earth’s planetary neighbour.
The six-wheeled rover, while navigating a 6.1-kilometre stretch within Jezero Crater, detected geological formations up to 35 metres underground. Jezero Crater, situated in the Martian northern hemisphere, is a region long believed to have once been a vast lake, teeming with water. Perseverance’s sophisticated instruments identified layered sediments and eroded surfaces that are hallmarks of a delta environment. These fan-shaped deposits of sediment are typically formed where a river meets a larger body of water, such as a lake. Scientists estimate this now-submerged delta dates back approximately 3.7 to 4.2 billion years. Considering that Mars, much like Earth, formed around 4.5 billion years ago, this delta represents a very early chapter in the Red Planet’s history.
This newly discovered delta predates another, more superficial delta in the vicinity, known as the Western Delta, which is estimated to be between 3.5 and 3.7 billion years old.
The key to this groundbreaking discovery lies in the rover’s RIMFAX (Radar Imager for Mars’ Subsurface Experiment) instrument. RIMFAX works by sending radar pulses into the Martian ground and analysing the signals that bounce back from underground features. This process allows for a detailed three-dimensional map of the subsurface. The latest findings are derived from the deepest data ever collected by RIMFAX, gathered over 250 Martian days, from September 2023 to February 2024.
The ongoing search for evidence of past life on Mars is heavily reliant on understanding the planet’s history of water. Mars, currently a cold and barren world, is thought to have once possessed a thicker atmosphere and a warmer climate, conditions conducive to the presence of liquid water on its surface.
“From the features mapped by RIMFAX, we believe that Jezero Crater hosted an ancient water-rich environment, capable of biosignature preservation that existed prior to the formation of Jezero’s Western Delta,” stated Emily Cardarelli, a planetary scientist at UCLA and a member of the Perseverance science team. Cardarelli, who led the research published in the journal Science Advances, highlighted the significance of this finding.
A biosignature refers to any physical or chemical evidence that could indicate the presence of past or present life. On Earth, river deltas are recognised as prime locations for concentrating sediments and creating environments that are highly favourable for microbial life.
Last year, scientists announced that a rock sample collected by Perseverance within Jezero Crater contained a potential biosignature. While this sample hinted at the possibility of ancient microbial life, it’s important to note that the minerals identified can also form through non-biological processes. That particular rock sample was dated to roughly 3.2 to 3.8 billion years ago.
Perseverance has been actively exploring Jezero Crater since its arrival in 2021. The prevailing scientific theory suggests that ancient river channels once flowed over the crater’s rim, feeding a substantial lake within.
David Paige, a planetary scientist at UCLA and co-author of the study, expressed his excitement about the RIMFAX data. “It’s very exciting that RIMFAX was able to provide such a detailed view of these deposits, and thus help solve the puzzle of their origin,” Paige commented. He further emphasised the value of ground-penetrating radar as an indispensable tool for studying planetary geology.
This discovery on Mars echoes similar findings from other space missions. Last year, Chinese scientists reported that the Zhurong rover, employing its own ground-penetrating radar, detected subsurface evidence in Mars’ northern plains that resembled sandy beaches. This suggested the possible existence of an ancient ocean in that region.
“Over time, we’ve seen more and more evidence for liquid water on the Martian surface at various rover landing sites, areas we’ve traversed to, as well as from orbital imagery,” Cardarelli observed. “We have seen channels where water may have flowed, crater lakes where water once ponded, and deltaic sediments deposited as rock outcrops and now as buried remnants, with this (research) paper.”
The ongoing exploration of Mars continues to reveal the planet’s complex and diverse history. “Mars is diverse, and each rover mission reveals another piece of its puzzling past and the early development of our rocky neighbor,” Cardarelli concluded. The uncovering of this ancient, buried delta significantly enhances our understanding of Mars’s hydrological evolution and its potential to have harboured life.
