The Perseverance rover is collecting rock samples from Mars to bring back to Earth

Hidden within the minerals and textures that make up rocks are clues about how and after they fashioned and had been later altered. These modifications can happen as a result of presence of water-rich fluids and may additionally be influenced by organic processes.

We’re planetary petrologists (rock scientists) and collaborating scientists on the Mars 2020 Perseverance rover mission. Our analysis entails exploring and deciphering the info despatched again by the Perseverance rover from its landing site in Jezero Crater.

A mysterious lake

Orbital photographs present that Jezero Crater was as soon as the location of a standing physique of water. It held a lake that was fed by water from an ~170 km-long river channel, and pictures present a delta—a fan-shaped platform of sediment—on the mouth of the channel. This delta is made up of layers of finer sediments combined with boulder-rich layers that recommend that the river flow fluctuated from relatively calm conditions to large floods.

Extra of a thriller, nevertheless, had been rock models uncovered in Jezero Crater’s flooring, the place Perseverance landed on Feb. 18, 2021. Of explicit curiosity was an enigmatic unit, recognized by the presence of olivine its spectral signatures (measurements of the quantity of radiation it displays).

Proof of historical past

Olivine is a vitreous, inexperienced mineral (its gem selection is peridot) that normally crystallizes in high-temperature magmas. In distinction, carbonate minerals can kind from excessive to low temperatures, normally from melts or fluids that may have been favorable for life.

The olivine-rich unit is widespread within the area past Jezero, covering approximately 70,000 square kilometers, and uncovered throughout the crater simply to the north and west of Perseverance’s landing site, in a region dubbed Séítah.

Séítah (meaning “amidst the sand” in Navajo) is roofed by a community of sand dunes, making it troublesome for the rover to navigate. Nonetheless, it was thought of a compelling goal for understanding the historical past of this area of Mars and since its carbonate minerals may protect proof of historic life.

Perseverance entered Séítah in September 2021 and readily confirmed the incidence of olivine by its remote-sensing instruments. The microscopic cameras noticed two- to three-millimeter olivine grains, however their origin was unknown.

On Earth, olivine grains of this measurement and form could also be concentrated by varied geologic methods, together with as wind- or water-borne sands sourced from olivine-rich areas, explosive volcanic eruptions, materials ejected by meteorite influence, or they will kind as crystals in cooling magma.

Extra data was wanted to interpret the historical past of the olivine, however engineering challenges initially impeded the mission’s potential to make use of its X-ray fluorescence (XRF) spectrometer on Séítah rocks.

Refined tools

XRF spectrometers have been necessary devices for figuring out the basic compositions (sodium to iron, and a few hint parts) of rock surfaces on Mars.

Alpha Particle X-ray Spectrometers (APXS) onboard Pathfinder, the two Mars Exploration Rovers Spirit and Opportunity, and the Mars Science Laboratory rover Curiosity offered bulk chemistries of ~1.5 cm round spots that helped geologic interpretations.

However for some Martian rocks, uncertainties have lingered about small-scale options and positive rock textures which might be vital for deciphering what minerals are current, whether or not they’re igneous or sedimentary, or their alteration histories.

The PIXL onboard Perseverance is a big improvement in this regard: PIXL generates ~120 micron grid maps that not solely present rock and mineral chemistries, however textures that can be utilized to deduce the origin, processes and relative timing of the varied minerals and different elements current.

The primary PIXL scan of a rock floor at a Séítah outcrop called Brac finally nailed the unit’s origin as igneous. The olivine grains are well-formed crystals with straight edges. Different high-temperature minerals, together with feldspar, and bigger minerals enclose or happen within the areas between the olivine crystals, indicating sluggish cooling of a magma.

Brac is a sort of rock referred to as an olivine cumulate that fashioned when olivine crystallized close to the highest of a magma, and settled and accrued downward attributable to its increased density. Olivine cumulates are well-known to kind on Mars as a result of they’re discovered among the many Martian meteorites, comprising a bunch known as chassignites, that was ejected from Mars by an influence occasion and finally fell to Earth.

On Earth, olivine cumulates happen in giant layered intrusions, such as the Skaergaard Intrusion in East Greenland, and in thick lava flows, such as found in the Abitibi, Ont. area.

Anticipating core samples

As exceptional because the PIXL scans are, Perseverance is supplied with a very sophisticated sampling tool, which it used to gather cores of Brac. Not less than considered one of these core samples will probably be delivered to Earth within the early 2030s as a part of the Mars Sample Return effort.

Mars Pattern Return would allow researchers at Earth-based labs to look at options right down to the nanoscale, which may yield details about crystallization historical past, water exercise within the rock and the way lengthy the rock was uncovered. This might present clues in regards to the historical past of life on Mars.

Radiometric isotopic analyses would assist pinpoint the timing of crystallization. Secure isotopes (H, C, N, O) would inform us in regards to the historical past of fluids on Mars. The list goes on and on.

Returned samples would allow us to reply the questions which might be hinted at by the the current PIXL outcomes. We may then present a fuller historical past of the olivine and carbonate-rich rocks in Jezero, and what they inform us about Mars’ historical past and potential for all times.

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