DUGWAY, UTAH – SEPTEMBER 24: In this document provided by NASA, from left, NASA … (+)
It is humbling to realize that we are the first sentient beings to have successfully sampled Bennu, a 500 meter asteroid that has been around even longer than planet Earth. Samples taken from carbon-rich Bennu are already providing new clues about the ubiquity and diversity of chemical compounds in our early solar system.
But a page-turning new book offers a detailed look at how such missions are carried out.
In The Asteroid Hunter: A Scientist’s Journey to the Dawn of Our Solar SystemDante Lauretta deftly chronicles his journey from college-aged short-order cook to one of the principal architects of a space mission that represents one of the landmark scientific achievements of the 21st century.
The story of the mission dates back to an informal meeting over drinks with a Lockheed Martin executive, the director of the University of Arizona’s Lunar and Planetary Laboratory, and Lauretta in the bar of an upscale hotel from Tucson. In just a few minutes, Lauretta had outlined the basic concepts of what would become OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer).
Less than two decades after that first meeting at the cocktail bar, OSIRIS-REx had successfully returned a 4.5 billion-year-old sample of Bennu and delivered it safely to the Utah desert. There, Lauretta and her colleagues eagerly awaited the return of the intact sample.
What did the mission on Bennu teach us?
That Bennu is a fragment of a much larger object that was shattered in the main asteroid belt about a billion years ago, Lauretta, principal investigator of OSIRIS-REx and an astrobiologist at the University of ‘Arizona in Tucson,’ he told me over the phone. . This object was about 200 km in diameter and came from much further out in the solar system, probably around where Saturn currently resides, he said. All the basic elements of life are found in this object, Lauretta says, and its parent was probably either an ocean world or a muddy world very early in the history of the solar system.
Ancient clay mud
Bennu’s parent asteroid must have been a giant convecting ball of mud, circulating fluid for millions of years and completely changing the original mineralogy, Lauretta writes in The Asteroid Hunter.
Bennu likely broke off from a much larger, carbon-rich asteroid about 700 million to 2 billion years ago, according to NASA.
Low density object
Most asteroids in the inner solar system are stony, high-density, close-to-Earth objects, Lauretta explains. But Bennu is much more porous and much less dense than we expected, he says.
Why are asteroids so important for understanding life in the solar system?
If you start trying to piece together the history of our planet, you get to a point, about 4 billion years ago, where there are no traces of rock left, Lauretta says. You have to go to asteroids to understand all the way back to the very beginnings of minerals, organic matter and ice formation in our solar system, he says. They are home to the earliest stages of the solar system’s evolution, he notes.
A sturdy surface
Bennu’s surface was much more rugged and rocky than our analysis of the telescope data predicted, Lauretta says. We thought it would be sand, or maybe gravel, and it was just dominated by these giant rocks, he said.
Example of surprise
Upon analysis, the phosphates found on Bennu look like evaporations from an ancient ocean world, much like an icy satellite we see around Saturn, Lauretta says. And we’re really excited about the diversity of organic materials, he says.
Why is phosphorus so essential for life?
The two rails that form the double helix structure of DNA are phosphates linked to sugars, Lauretta explains. Phosphate is therefore essential for the manufacture of DNA and RNA, he notes. It’s also a very important element for the energy-carrying molecule called Adenosine triphosphate (ATP), explains Lauretta, since the P stands for phosphate. And then, in animals like us, phosphate minerals also make up our bones and teeth, he says.
In terms of mass, phosphorus is the fifth most important biological element, after hydrogen, carbon, oxygen and nitrogen, Lauretta writes in her book. But where terrestrial life gets its phosphorus remains a mystery, he writes.
The Asteroid Hunter
An abundance of amino acids
We found 13 of the 20 amino acids used in biology in our samples, explains Lauretta.
As for the other seven?
We can’t rule them out yet, perhaps they were below our current detection limit, explains Lauretta. We also found the four nucleic acid bases or letters of the genetic code used in DNA; This means that Earth received these compounds from these carbon-rich asteroids, he says.
The samples could even reveal some sort of microfossils or evidence of past life if they are there.
It’s something we pay a lot of attention to, says Lauretta, but we’re missing something fundamental to understanding the origin of life. He particularly wonders what happens when you go from a simple geological material to something living. Lauretta is also perplexed as to why molecules self-organize into living organisms with self-preservation instincts and the ability to respond to their environment.
As for OSIRIS-REx?
About 20 minutes after the OSIRIS-REx spacecraft released its sample return capsule into Earth’s atmosphere, the spacecraft started its engines to embark on a new mission, NASA said. Renamed OSIRIS-Apophis Explorer, the spacecraft is expected to reach the asteroid Apophis in 2029.