Space News & Blog Articles

Earth is the only life-supporting planet we know of, so it’s tempting to use it as a standard in the search for life elsewhere. But the modern Earth can’t serve as a basis for evaluating exoplanets and their potential to support life. Earth’s atmosphere has changed radically over its 4.5 billion years.

A better way is to determine what biomarkers were present in Earth’s atmosphere at different stages in its evolution and judge other planets on that basis.

That’s what a group of researchers from the UK and the USA did. Their research is titled “The early Earth as an analogue for exoplanetary biogeochemistry,” and it appears in Reviews in Mineralogy. The lead author is Eva E. Stüeken, a PhD student at the School of Earth & Environmental Sciences, University of St Andrews, UK.

When Earth formed about 4.5 billion years ago, its atmosphere was nothing like it is today. At that time, the atmosphere and oceans were anoxic. About 2.4 billion years ago, free oxygen began to accumulate in the atmosphere during the Great Oxygenation Event, one of the defining periods in Earth’s history. But the oxygen came from life itself, meaning life was present when the Earth’s atmosphere was much different.

This isn’t the only example of how Earth’s atmosphere has changed over geological time. But it’s an instructive one and shows why searching for life means more than just searching for an atmosphere like modern Earth’s. If that’s the way we conducted the search, we’d miss worlds where photosynthesis hadn’t yet appeared.

Multiple space agencies are looking to send crewed missions to the Moon’s southern polar region in this decade and the next. Moreover, they intend to create the infrastructure that will allow for a sustained human presence, exploration, and economic development. This requires that the local geography, resources, and potential hazards be scouted in advance and navigation strategies that do not rely on a Global Positioning System (GPS) developed. On Sunday, April 21st, the Chinese Academy of Sciences (CAS) released the first complete high-definition geologic atlas of the Moon.

This 1:2.5 million scale geological set of maps provides basic geographical data for future lunar research and exploration. According to the Institute of Geochemistry of the Chinese Academy of Sciences (CAS), the volume includes data on 12,341 craters, 81 impact basins, 17 types of lithologies, 14 types of structures, and other geological information about the lunar surface. This data will be foundational to China’s efforts in selecting a site for their International Lunar Research Station (ILRS) and could also prove useful for NASA planners as they select a location for the Artemis Base Camp.

Credit: CAS via Xinhua handout

Ouyang Ziyuan and Liu Jianzhong, a research professor and senior researcher from the Institute of Geochemistry of the CAS (respectively), oversaw these efforts. Since 2012, they have led a team of over 100 scientists and cartographers from relevant research institutions. The team spent more than a decade compiling scientific exploration data obtained by the many orbiters, landers, and rovers that are part of the Chinese Lunar Exploration Program (Chang’e), and other research about the origin and evolution of the Moon.

According to the CAS, the atlas includes an “upgraded lunar geological time scale” for “objectively” depicting the geological evolution of the Moon, including the lunar tectonics and volcanic activity that once took place. As a result, the volume could not only be significant in terms of lunar exploration and site selection. Still, it could also improve our understanding of the formation and evolution of Earth and the other terrestrial planets of the Solar System – Mercury, Venus, and Mars. As Jianzhong indicated in a CAS press release,

Last November, NASA’s Lucy mission conducted a flyby of the asteroid Dinkinish, one of the Main Belt asteroids it will investigate as it makes its way to Jupiter. In the process, the spacecraft spotted a small moonlet orbiting the larger asteroid, now named Selam (aka. “Lucy’s baby”). The moonlet’s name, an Ethiopian name that means “peace,” pays homage to the ancient human remains dubbed “Lucy” (or Dinkinish) that were unearthed in Ethiopia in 1974. Using novel statistical calculations based on how the two bodies orbit each other, a Cornell-led research team estimates that the moonlet is only 2-3 million years old.

The research was led by Colby Merrill, a graduate student from the Department of Mechanical and Aerospace Engineering at Cornell. He was joined by Alexia Kubas, a researcher from the Department of Astronomy at Cornell; Alex J. Meyer, a Ph.D. student at the UC Boulder College of Engineering & Applied Science; and Sabina D. Raducan, a Postdoctoral Researcher at the University of Bern. Their paper, “Age of (152830) Dinkinesh-Selam Constrained by Secular Tidal-BYORP Theory,” recently appeared on April 19th in Astronomy & Astrophysics.

Merrill was also part of the NASA Double Asteroid Redirection Test (DART) mission, which collided with the moonlet Dimorphos on September 26th, 2022. As part of the Lucy mission, Merrill was surprised to discover that Dinkinesh was also a binary asteroid when the spacecraft flew past it on November 1st, 2023. They were also fascinated to learn that the small moonlet was a “contact binary,” consisting of two lobes that are piles of rubble that became stuck together long ago.

Artist’s Rendering of NASA’s Lucy mission, which will study asteroids within the Main Belt and Jupiter’s Trojan population. Credit: Southwest Research Institute

While astronomers have observed contact binaries before – a good example is the KBO Arrokoth that the New Horizons spacecraft flew past on January 1st, 2019 – this is the first time one has been observed orbiting a larger asteroid. Along with Kubas, the two began modeling the system as part of their studies at Cornell to determine the age of the moonlet. Their results agreed with one performed by the Lucy mission based on an analysis of surface craters, the more traditional method for estimating the age of asteroids. As Merrill said in a recent Cornell Chronicle release: