How Dinosaur Hunter Mary Anning Went To Mars

Tuesday, December 1, 2020

Curiosity poses for the ultimate tourist selfie. NASA/JPL

When Victorian paleontologist Mary Anning walked along the limestone cliffs of southwest England 200 years ago, she probably never dreamed that future scientists would name a piece of Mars in her honor. It’s quite a small piece of Mars: a patch of clay-bearing rock where the Curiosity rover drilled three holes in search of organic molecules. Two of those holes, dubbed Mary Anning and Mary Anning 3, were named in honor of the groundbreaking paleontologist who discovered the first fossil ichthyosaur. 

Anning’s hunting ground was the coast of the English Channel, where the landscape of southern England meets the sea in steep walls of limestone. The rocks of those cliffs were laid down during the Jurassic period, between 200 million and 145 million years ago, when southwest England lay at the bottom of the sea instead of overlooking it. From the crumbling layers of ancient seabed, Anning unearthed the fossilized bones of the long-extinct reptiles that once prowled the Jurassic seas.

This species of ichthyosaur , Ichthyosaurus Anningae is named in honor of Mary Anning. BY NOBU TAMURA

In 1810, she found and excavated the nearly complete skeleton of a 5.2 meter-long ichthyosaur, a marine reptile which bears an uncanny resemblance – but only a distant relation – to modern swordfish. It’s a perfect example of convergent evolution; ichthyosaurs and swordfish aren’t closely related, but they live similar lives in similar environments, so they eventually evolved similar shapes. Over the years, Anning found several other nearly complete ichthyosaur skeletons, along with loose fossils, in the cliffs of Dorset County.

She also discovered the nearly complete remains of two plesiosaurs in 1820 and 1830, and in 1828 she unearthed the first pterosaur ever found outside Germany. During the winter, landslides would send parts of the cliffs tumbling to the beach below, revealing new fossils. Anning had to work quickly to retrieve the fossils, because rising tides would wash the finds away almost as quickly as they’d been revealed. It was dangerous work; in 1833, Anning was on the beach with her dog Tray when rocks crashed down from the cliff above. Anning narrowly escaped; Tray didn’t make it.

Today, Anning is best known as the discoverer of the ichthyosaur, but she also identified several new species of fossil fish and invertebrates. She was also one of the scientists who helped prove that coprolites were actually fossilized poop.

Sexism held Anning back from publishing descriptions or analysis of the fossils she discovered, but many of the same paleontologists who would have balked at seeing her name in print had no scuples about publishing their own studies of her fossil finds. Several male geologists and paleontologists made names and careers on Anning’s work, but only one ever gave her even partial credit.

During her lifetime, two species of fossil fish were named in Anning’s honor, but most of the recognition she has received has been more recent. Now she can claim a species of ichthyosaur, an entire genus of plesiosaurs, and a genus of therapsids (extinct reptiles which were the distant ancestors of today’s mammals), along with a species of tiny shrimp called ostracods and a genus of bivalve molluscs. And, of course, there are those two drill holes in a slab of bedrock on Mars.

The third hole, Grokken, is named for a fossil-bearing region in Scotland. NASA/JPL

The site looks like the sort of place Anning might have hunted for fossils. It’s part of a region NASA calls Glen Torridon, and billions of years ago it was filled with lakes and streams, which left behind clay and organic molecules. Those molecules aren’t evidence of life, but they definitely suggest that the building blocks of life were available. That’s why Curiosity stopped and took three samples of the clay-rich bedrock in July 2020. Instruments aboard the rover and back on Earth are still analyzing the chemistry of those samples, hoping to learn more about the early Martian environment.

Meanwhile, Curiosity paused in late October to take a selfie with the scenic spot (planetary geologist Michelle Minitti described it in July as “a large, lovely, layered block”) before continuing its long climb up the slope of Mount Sharp. Selfies with the rover’s Mars Hand Lens Imager, or MAHLI, are much more complicated than the selfies Earthbound tourists take with their smartphones. MAHLI is mounted on the end of Curiosity’s robotic arm, and it took weeks of work to stitch 59 separate images together into the version NASA published earlier in November 2020.

Curiosity is now well on its way to its next stop, a layer of sulfate-rich rock further up the mountain, which it should reach in early 2021.

Meanwhile, in a mission update earlier this year, Minitti wrote, “Let Mary Anning’s name on Mars remind us to include everyone in the endeavor of exploration.”