Scientists involved with the Perseverance rover mission announced at the Lunar and Planetary Sciences Conference that the rover has successfully filled 26 out of its 43 sample tubes on the Martian surface. Meenakshi Wadhwa, a planetary scientist at Arizona State University and principal scientist for Mars Sample Return (MSR), revealed that 20 of the tubes contain rock cores, while two contain regolith and another holds a sample of the atmosphere. The remaining three are "witness tubes" used for control purposes to identify potential terrestrial contamination.

The rover is currently traversing the remains of a river delta in Jezero Crater, with plans to explore the crater rim next, which is expected to provide a diverse range of rocks of different ages and exposure to various processes, including materials with astrobiological potential.

Meanwhile, NASA is in the final stages of reviewing its MSR architecture, including the schedule and design of the mission that will bring back the collected sample tubes to Earth. After an independent review board determined that the agency's existing approach couldn't meet cost and schedule goals, a Mars Sample Return IRB Response Team (MIRT) was commissioned in October to evaluate alternative approaches. Wadhwa mentioned that the MIRT's assessment is nearing completion, and NASA intends to release its revised MSR plans, along with a proposed budget, in April.

The uncertainty surrounding the MSR mission has put NASA's overall planetary science portfolio in limbo. The agency's fiscal year 2025 budget request left MSR funding as "to be determined." However, an appropriations bill passed on March 8 provides funding of at least $300 million, up to $949.3 million, for MSR in fiscal year 2024. Lori Glaze, director of NASA's planetary science division, explained that the TBD in the fiscal year 2025 budget request reflects the need to wait for the MIRT's assessment before requesting specific funding.

NASA officials stressed the scientific significance of the Mars Sample Return mission, which has been recognized as a top priority in recent decadal surveys. Lindsay Hays, acting lead scientist for MSR at NASA Headquarters, referred to the samples as a "Rosetta Stone" that could unlock the early history of terrestrial planets.

However, the uncertainty surrounding the MSR mission has caused challenges in science planning. The Perseverance rover's potential future surveys beyond the crater rim to collect additional samples are on hold pending the MIRT's results. Both Wadhwa and Hays emphasized the importance of maximizing sample number and diversity for the mission.

As the MIRT's assessment nears completion, it will shape the timeline and traverse plans for Perseverance to collect samples at and beyond the crater rim, where an incredible range of rocks awaits further exploration.

With the release of the revised MSR plans and budget due next month, the future of the Mars Sample Return mission and its place within NASA's overall planetary science portfolio will become clearer. The agency aims to strike a balance between supporting Mars Sample Return and other important planetary programs under a limited budget.