Astrobites at AAS 242: Day 4

Welcome to the summer American Astronomical Society (AAS) meeting in Albuquerque, NM, and online! Astrobites is attending the conference as usual, and we will report highlights from each day here. If you’d like to see more timely updates during the day, we encourage you to search the #AAS242 hashtag on Twitter. We’ll be posting once a day during the meeting, so be sure to visit the site often to catch all the news!

The site of the Perseverance Mars rover’s first sample collection. (NASA/JPL-Caltech/ASU/MSSS)

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Plenary Lecture: Meenakshi “Mini” Wadhwa (Arizona State University) (by Lucas Brown)

The final plenary lecture of AAS 242 was given Thursday morning by Dr. Meenakshi “Mini” Wadhwa from Arizona State University on the role of sample return missions in exploring the past and present of our solar system. From Apollo to Mars Sample Return, these missions have and will continue to provide unique and invaluable insight into the formation of our solar system, the origins of life, and beyond.

Sample return missions, which are missions to collect material directly from extraterrestrial sources, have existed since the 1960s, beginning with the Apollo missions. While it has been possible to study extraterrestrial materials for much of human history through examining meteorites which land on the surface of Earth, the utility of meteorites is limited by the fact that we don’t have direct context for their origins; where a particular meteorite originated from in the solar system is often unknown. Additionally, when these objects come into contact with Earth’s atmosphere and surface, their properties and composition can change relative to when they were floating through space. On the other hand, space missions are limited in how much analysis they can do due to constraints on the size and mass of satellites that can be launched on existing rockets. Dr. Wadhwa explained that bringing samples back enables higher resolution and more precise analyses, and it also allows for experiments to be reproduced across numerous labs and with multiple techniques — all increasing the reliability of the results. Additionally, sample return missions greatly increase the number of researchers who can be involved in analysis, and these missions can inspire the broader public. To give a specific example of the impact of a past sample return mission, the return of lunar regolith and rock samples during the Apollo missions led to the finding of the first evidence of magma oceans in the Moon’s early formation history, which is now foundational in many theories attempting to explain the formation history of rocky planets.

While many robotic sample return missions have occurred in the decades since Apollo, Dr. Wadhwa focused much of her talk on Hayabusa2, a Japanese mission launched in 2014 to the asteroid Ryugu. This mission not only orbited and mapped the asteroid, but also landed on its surface several times, collecting samples of subsurface material by launching copper projectiles into the surface and collecting the ejected material in internal compartments. Through work done in part by Dr. Wadhwa and her collaborators, careful analysis of the composition of the asteroid was performed, including analysis of the titanium, chromium, and strontium isotopes present in the Ryugu samples. Understanding the presence of these elements can help us understand the distribution of materials in the protoplanetary disk from which our solar system formed, and it also allows us to determine the age of the asteroid, which closely matches the estimated age of the solar system (around 4.5 billion years).

Still image from a video depicting the Hayabusa2 spacecraft launching a projectile at the surface of Ryugu, creating a cloud of debris
Still image from a video taken by the Hayabusa2 spacecraft depicting the cloud of debris ejected from the surface of asteroid Ryugu after the spacecraft launched a copper projectile into it. The spacecraft was able to collect subsurface material from this cloud of debris, later returning the material to Earth for analysis. (Credit: JAXA)

Looking ahead to the future, Dr. Wadhwa spoke about Mars Sample Return (MSR), a proposed multi-step, multi-vehicle, multi-agency mission to return material from the surface of Mars. While such a mission has been proposed for many decades now, always claimed to be just “10 years away,” there now exists real funding and extensive planning to make this a reality within the next 10 years (for real this time). In fact, Perseverance — NASA’s newest rover, which landed on the surface of the red planet in 2021 — has already begun the process of collecting interesting sample material, dropping sample canisters along the way for future missions to retrieve. Such a retrieval will require the launch of additional spacecraft, one of which will land on the surface, intake the sample canisters, and then launch them into orbit with an on-board miniature rocket. The samples, once in orbit, will be retrieved by another craft and flown back to Earth. This plan is complex, introducing many never-before-demonstrated procedures, such as the ability to launch a payload into orbit from the surface of another planet. The intense efforts involved in MSR go to show the immense interest that exists within the scientific community for sample return missions.

Image showing the samples of Martian material which have already been collected and deployed on the surface by the Perseverance rover.
An ambitious plan is in the works to return samples of material from the surface of Mars known as Mars Sample Return. The Mars Perseverance rover has already collected samples into sealed canisters which have been deposited onto the surface for later retrieval. One such canister is visible in the foreground of this photo, with the location of others also being highlighted. (Credit: NASA/JPL-Caltech/ASU/MSSS)

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