Water in Space? New Findings From Asteroid Sample May Point Toward Origins of Life

November 2, 2023
Science Magazine

Life from Space

Early Earth was a fiery landscape; temperatures of 3,000 degrees Celsius, an atmosphere devoid of oxygen, and the constant crashing of asteroids characterized this hellish environment. What could have sparked the development of life on our planet?

Ever since NASA shockingly discovered microscopic organic compounds in a meteorite that fell to Earth in 2000, some scientists have theorized that the answers to questions about the origins of life lie within ancient asteroids. Now, new meteor samples from an asteroid dubbed Bennu may provide even more evidence to support this idea.

Above: The asteroid Bennu, captured by the OSIRIS-REx spacecraft. Image courtesy of NASA.

The OSIRIS-REx Mission

The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer, better known as the OSIRIS-REx spacecraft, was developed by scientists from the University of Arizona and first launched on September 8th, 2016 from the historic site of Cape Canaveral, Florida. Armed with a host of measurement equipment including an IR Spectrometer, X-Ray Imaging, and a Touch-And-Go Sample Acquisition Mechanism, OSIRIS-REx left Earth to collect a sizable physical sample from Bennu. 

Above: Bennu’s size compared to landmarks. Image courtesy of University of Arizona

Slightly taller than the Empire State Building at a height of 510 meters, Bennu is a relatively small asteroid that passes by Earth every six years and circles the Sun in the same orbit as Earth. Captivating the interest of many scientists, Bennu likely originated around 4.6 billion years ago when the solar system first formed. Telescope analysis of Bennu found that it is rich with carbon, a necessary component for basic organic compounds as well as more complex amino acids and proteins. Thus, scientists have long considered Bennu as a potential source of evidence on the origins of life.

Eleven days after its initial launch in 2016, OSIRIS-Rex used its rocket propellers to establish an orbit around Earth and begin its scientific measurements.The spacecraft then began firing its thrusters to orient itself towards Bennu. In 2018, through the use of an Earth gravity-assist encounter—a procedure where a spacecraft uses Earth’s gravity to change its path and speed—OSIRIS-REx finally arrived at Bennu. While scientists were initially concerned that OSIRIS-REx would crash on Bennu’s unusually rocky and jagged surface, the spacecraft actually sank into the asteroid, which had a consistency similar to thick mud. On Bennu, OSIRIS-REx spent two years searching for a suitable data collection site and gathering samples. Finally, after a complex return involving two revolutions around the Sun, the spacecraft returned the sample to Earth in 2023. After dropping off the sample capsule in the Utah desert, OSIRIS-REx returned to space to pursue Apophis, an asteroid that will be in range of Earth in 2029. 

What did the mission find?

Above: The return of the OSIRIS-REx sample capsule. Image courtesy of NASA.

When OSIRIS-REx’s sample finally returned on September 24, 2023, the astronomy community was ecstatic. Astrobiologist Daniel Glovin commented that the sample was “an astrobiologist’s dream.” After thorough analysis of the ancient black dust by scanning electron microscopes and X-rays, researchers at NASA and other institutions found that Bennu is rich in not only carbon but also water within its minerals. In addition to a composition of five percent carbon, analysts also found one of the main elemental building blocks for life—sulfide minerals, a necessary component for planetary biological evolution—in the sample. The abundance of water in the asteroid sample—and the high carbon content that could help form complex organic molecules—could support the idea that extraterrestrial rocks once brought the optimal components for life to Earth.

Above: Black dust that makes up the OSIRIS-REx sample. Image courtesy of BBC.

While analysis of the asteroid samples brought back by OSIRIS-REx has already revealed shocking results, researchers still have much information to gather from the sample. The NASA team has yet to fully clear out the inner chamber of the spacecraft capsule, which holds the fragments and pieces of Bennu. In the coming weeks, NASA will distribute portions of these samples to researchers from all over the world. While research on Earth will continue to make exciting discoveries with the spacecraft’s first round of samples, OSIRIS-REx’s new purpose in space may provide more news yet to come. Stay tuned for its return in 2029 to find out!

Will Sun

Will (Trinity ’27) is originally from San Jose, California and plans on majoring in Biology. In his free time, he enjoys collecting keychains, playing basketball, and going on walks.

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