Free Astronomy Magazine January-February 2023

10 JANUARY-FEBRUARY 2023 ASTRO PUBLISHING T his pair of images shows two cylinders of rock the size of classroom chalk inside the drill of NASA’s Perseverance rover from an outcrop called “Wildcat Ridge” in Mars’ Jezero Crater. The image of the rock core on the left, called “Hazeltop,” was taken by Perseverance’s Mastcam-Z instrument on July 25, 2022, the 509 th Martian day, or sol, of the mission. The image on the right, of the rock core called “Bearwallow,” was taken on Aug. 2, 2022, the 516th sol. Each core is about 0.5 inches, or 13 millimeters, in diameter and 2.4 inches, or 60 millimeters, long. They were taken from an ancient river delta in Jezero Crater, a fan-shaped area where, billions of years ago, a river once flowed into a lake and deposited rocks and sediment. Sci- entists interpret these rocks to be fine-grained sedimentary rocks. They appear to have formed under saltwater conditions, possibly as water from the crater’s ancient lake was evaporating. These rock cores have been sealed in ultra-clean sample tubes and stored in Perseverance’s Sampling and Caching System as part of the mission’s search for ancient signs of micro- bial life. The verification of ancient life on Mars carries an enormous burden of proof. [NASA/JPL-Caltech/ASU/MSSS] Raman & Luminescence for Organics & Chemicals) apparatus onboard Percy. Like the discovery of “the most distant galaxy ever” or “the largest prime number yet discov- ered,” we await Percy’s arrival at a new location in the Jezero delta where such organic molecule con- centrations may be considerably higher still. Unfortunately, the equipment onboard Perseverance does not allow for the detailed char- acterization of the types and variety of molecules collected on the sur- face. The molecules might have been ancient waste products of bio- logical processes or the molecular debris of long-extinct living organ- isms. Alternatively, these organics might be the small, simple molecular species for which time, radiation, and chemistry might have eventually produced the right conditions for the earliest of biologically relevant processes to occur if Mars had not gone from life-sustaining to dry and inhospitable on its surface over three billion years ago. These mole- cules might also simply have been deposited and concentrated as the ancient river delta dried up during the transition of the river delta, and Mars itself, to what we know it as today, with the right conditions for life or its pre-biotic chemical under- pinnings never having been achieved at all. The problem with simple molecules is that both biological and non-bio- logical processes are equally capable of producing them – the existence of methanol and ethanol both in our bodies and in the cold vacuum of in- terstellar clouds is certainly proof of this point. Without invoking a higher power, hyperdimensional alien seeding, or a rather complex time travel scenario, it can be stated with very high confidence that the chemistry of life did not begin with proteins and DNA, but that larger and more complex molecules are one of the key steppingstones on the road to life as we know it. At our current level of understanding, we simply do not know if the organic molecules we’ve detected might have been the eventual cause of life on Mars, the products of living processes on Mars, or of absolutely