A GIFT FROM THE COSMOS

EVERY YEAR, TENS of thousands of meteorites survive trips through our atmosphere to reach Earth. But the one that struck in the Costa Rican rainforest last year was really special: This gift from the cosmos isn’t just any stone, it’s one that’s rich in the building blocks of life.

Joshua Sokol gives details in Science, August 14, 2020, https://science.sciencemag.org/content/369/6505/760. This particular space rock was sizable when it encountered the Earth’s atmosphere: about the size of a washing machine before it broke into fragments above central Costa Rica on April 23, 2019. 

Sokol reported that “dozens of fragments, chock full of primordial carbon, landed along a 6-kilometer-long swath between the villages of La Palmera and Aguas Zarcas.… Aguas Zarcas, as the fragments would soon collectively be called, is a carbonaceous chondrite, a pristine remnant of the early Solar System.” 

Carbonaceous Chondrite. Sokol notes that, “The vast majority of meteorites are lumps of stone or metal. But true to their name, carbonaceous chondrites are rich in carbon—and not just boring, inorganic carbon, but also organic molecules as complex as amino acids, the building blocks of proteins.”

“They illustrate,” he writes, “how chemical reactions in space give rise to complex precursors for life; some scientists even believe rocks like Aguas Zarcas gave life a nudge when they crashed into a barren Earth 4.5 billion years ago.”

A Previous Hit in 1969. A similar carbonaceous chondrite broke up over Murchison, an Australian cattle town. Geology students collected about 100 kilograms (some 220 lbs.) of “Murchison.” 

“To date,” Sokol writes, “scientists have recognized nearly 100 different amino acids in it, many used by organisms on Earth and many others rare or nonexistent in known life. Hundreds more amino acids have been inferred but not yet identified.” 

He continues, “Murchison also contained nucleobases, the building blocks of genetic molecules such as RNA, and in November 2019, researchers found a major component of RNA’s backbone: the sugar molecule ribose.” 

Sokol quotes Daniel Glavin, an astrobiologist at NASA’s Goddard Space Flight Center, saying, “We’re not detecting life itself, but the components are all there.”

Fresh Findings from Aguas Zarcas. “The 30 kilograms of primodial leftovers from Aguas Zarcas hold similar promise,” Sokol says. “But these new pieces are 50 years fresher than Murchison, allowing scientists to apply modern techniques to preserve and probe what amount to fragile lumps of unspeakably old clay. They could sniff out delicate organic compounds long evaporated from Murchison. They could hunt not just for amino acids and sugars, but also proteins, which have long been suspected but never confirmed in a meteorite.”

Aguas Zarcas’s Journey. Sokol observes, “Aguas Zarcas itself endured several billion more years of solitude, save for occasional smashups with other wayward space rocks. Based on its fiery trajectory through Earth’s atmosphere, caught on dashcams and volcano-monitoring cameras, researchers believe the unknown body ended up in the asteroid belt between Mars and Jupiter. Then one last collision splintered off a chunk, which spiraled in toward Earth, nearing the rotating globe just as Costa Rica spun into view on 23 April 2019.”

The Meteorite Business. The Science article also describes other aspects of this gift from the cosmos. Among them are its business dealings. The meteorite market is subject to a patchwork of laws: For instance, Australia, Canada, Chile, France, Mexico, and New Zealand consider meteorites cultural treasures that cannot be exported without permission. Sokol notes, “Costa Rica may soon restrict the trade as well.”

Prices of Aguas Farcas fragments have soared. Sokol writes, “Stones could fetch $200, even $400 per gram. Bidding wars ensued.” One family “used meteorite proceeds to repaint the house, replace the roof, expand their dairy barn, and buy new furniture and a car.”

A Part of the Family. Sokol concludes, “Campos Muñoz is still a holdout, maybe the last. She still has the big chunk that fell through her roof, which she hopes will end up in an exhibition. She wants more for it—she won’t say exactly how much—than dealers have offered. The hole in the roof remains. She had meant to fix it, but first came the meteorite hunting frenzy, then the rainy season, and now the pandemic. Plus, she knows these bits of collateral damage are valuable to collectors, too. ‘This hole in the roof and the damaged tables are part of our family now,’ she says.”

It’s not every family that receives a gift from the cosmos. ds 

© Dennis Simanaitis, SimanaitisSays.com, 2020