The Lucy spacecraft flies past the Trojan asteroid 617 Patroclus and Menoetius in this artist’s rendering.
Credit: NASA Goddard

It’s not every day that the National Aeronautics and Space Administration (NASA)  launches a new spacecraft. Their latest, named Lucy, was launched Oct. 16, 2021, from Cape Canaveral Space Force Station in Florida. Its mission? Explore the Trojan asteroid belt near the orbit of Jupiter. Lucy doesn’t have a crew, but the craft is equipped with powerful telescopes and cameras to gather information about the mysterious asteroids.

Lucy won’t be taking a direct path to Jupiter’s orbit, however. The spacecraft will use a series of gravity assists to help move it closer to its target. In a gravity assist, a spacecraft uses momentum gained from swinging by a planet to adjust its path and fling it toward a target.

After spending a year orbiting the sun, Lucy will return to Earth’s orbit for its first gravity assist in October 2022. This assist will set it on a course it toward Mars. In 2024, a second gravity assist will send Lucy towards the main asteroid belt, between the orbits of Mars and Jupiter. On this orbit, Lucy’s telescopes and cameras will capture images of asteroid 52246 Donaldjohanson. The probe should arrive at the Trojan asteroid belt by 2027.

Each of the asteroids in the Trojan belt is named after a different hero from the Greek epic the Iliad. The first Trojan Lucy will photograph is Eurybates in August 2027. Eurybates is unique because it has a smaller moon orbiting it, named Queta. Polymele will be photographed in September 2027, and Leucus and Orus will be photographed in April 2028 and November 2028, respectively. After that, Lucy will return to Earth for one more gravity assist. In 2033, Lucy will finish the mission by visiting the Trojan asteroids Patroclus and Menoetius. The spacecraft will remain in orbit around the asteroids, studying the asteroids for as long as it continues to function.

The Trojan asteroids were named after Greek myths, but what about Lucy? Usually, NASA uses acronyms for naming spacecraft. An acronym is a word that uses the first letter of each word in a phrase to create a new word, for example referring to the National Aeronautics and Space Administration as NASA.  In Lucy’s case, however, they named the craft after a fossilized skeleton found in 1974, in Ethiopia. Lucy wasn’t exactly a human – she represented a species of hominin called Australopithecus Afarensis. Hominins are a group of living things that includes human beings and early humanlike ancestors.

The expedition that found the skeleton Lucy was led by the anthropologist Donald Johanson and his student Tom Gray. An anthropologist is a scientist who studies humans and their close relatives. They were looking for fossils, and on Nov. 24, 1974, they found one of the most significant fossils to date. With 40 percent of her recovered, Lucy represents one of the most complete skeletons ever found from her time, dating to about 3.18 million years ago. When the team returned to their camp the night they found the first fossils, they celebrated their finding by listening to music and partying. One of the songs on repeat that night was “Lucy In The Sky With Diamonds,” a song by British rock band The Beatles. Pamela Alderman, a member of the team, gave the fossil hominid they found the nickname “Lucy” after the song. Just as Donald Johanson was the first to discover the fossil Lucy, the spacecraft Lucy will be the first to study asteroid 52246 Donaldjohanson, named in the anthropologist’s honor.

September 30, 2019

Last month, in late August, scientists published a description of a 3.8-million-year-old fossil skull, allowing people to gaze into the face of perhaps our earliest ancestor, Australopithecus anamensis. According to one researcher, the remarkable fossil is the most complete skull of the “oldest-known species” of the human evolutionary tree. The important fossil helps define the ancient human evolutionary family, but it also brings more questions to the often cloudy relationships among that family’s members.

Paleontologists discovered the near-complete skull of Australopithecus anamensis in Ethiopia in 2016. Credit: © Dale Omori, Cleveland Museum of Natural History

A. anamensis belongs to the hominin group of living things that includes human beings and early humanlike ancestors. A team of paleontologists led by Yohannes Haile-Selassie from the Cleveland Museum of Natural History found the hominin skull in 2016 at a site called Woranso-Mille in the Afar region of Ethiopia. The fossil, officially known as MRD-VP-1/1 (MRD for short), was discovered in two halves that fit together, making up a nearly complete skull. The skull’s position in volcanic sediments enabled scientists to determine its age—3.8 million years—with great precision. The anatomical features of the skull helped identify it as A. anamensis, one of the earliest known hominin species. This species was first identified from a handful of fossil skull fragments and other bones discovered at Lake Turkana in northern Kenya in the 1990’s. Those specimens are between 4.2 million and 3.9 million years old.

Scientists used the fossilized Australopithecus anamensis skull to create this image of one of humankind’s earliest ancestors. Credit: © John Gurche/Matt Crow, Cleveland Museum of Natural History

The MRD skull shows that A. anamensis had a small brain, a bit smaller than that of a modern chimpanzee. The skull more closely resembles an ape than a modern human, with a large jaw and prominent cheekbones, but the canine teeth are much smaller and more humanlike. And, like humans, A. anamensis walked upright on two legs. Sediments and other fossils show that the region where the skull was found was arid, but the ancient creature died in a vegetated area near a small stream that entered a lake.

The site in Ethiopia where MRD was discovered is not far from the village of Hadar, where fossils of another early hominin, Australopithecus afarensis, were first discovered in 1974. A. afarensis is known mainly from the partial skeleton of an adult female, the famous “Lucy,” found in deposits dating to about 3.2 million years ago. Other A. afarensis fossils date to nearly 3.8 million years ago, which suggests Lucy and her kind may have coexisted with A. anamensis.

Most scientists, however, think that Lucy and her kind evolved from A. anamensis, and that the transition occurred as one species disappeared and the other took over. Scientists now understand that A. anamensis could still be ancestral to Lucy, but that other A. anamensis populations continued to thrive unchanged as her neighbors. The prehistoric landscape of East Africa had many hills, steep valleys, volcanoes, lava flows, and rifts that could easily have isolated populations over many generations. Over time, the populations eventually diverged. Scientists think that one of these species eventually gave rise to Homo, the human genus.

June 10, 2015

Fossilized jaws and teeth discovered in northern Ethiopia belong to a previously unknown ancient human ancestor that lived 3.3 million years ago, according to scientists who announced the discovery in late May 2015 in the journal Nature. The new species, named Australopithecus deyiremeda by the scientists who described the fossil remains, lived at the same time and in the same region as another early human ancestor.

Yohannes Haile-Selassie, a paleoanthropologist at the Cleveland Museum of Natural History, holds casts of the jaws of Australopithecus deyiremeda, a new human ancestor species from Ethiopia. (Credit: Laura Dempsey, Cleveland Museum of Natural History)

The Ethiopian anthropologist Yohannes Haile-Selassie of the Cleveland Museum of Natural History in Ohio described the fossils, which were found at a site in the Afar region of northeastern Ethiopia. The scientists concluded that the fossils are from an early hominin. Hominins, also called hominids, are the scientific family that includes human beings and early humanlike ancestors. The site is about the same age and only a few miles from Hadar, where fossils of Australopithecus afarensis were first discovered by the anthropologist Donald C. Johanson in 1974.  A. afarensis was an early humanlike creature known in part from a famous fossil skeleton nicknamed “Lucy.” The two species are similar in their anatomy, but they can be distinguished by different shaped jaws. Haile-Selassie believes the fossil jaws and teeth belong to the same species as several fossil foot bones that were discovered at a nearby site in Ethiopia and described in 2012.

The scientists believe the fossils demonstrate that Lucy and her kind were only one of perhaps several hominin species that inhabited the forests and grasslands of East Africa more than 3 million years ago. Each species was adapted to a different habitat and likely had different anatomy and behavior, including how it moved around. However, scientists are not certain if any of these species are direct ancestors to modern humans.

Paleoanthropologists speculate that the distinct jaw shapes of A. deyiremeda and A. afarensis could mean that they used their teeth on different kinds of food. This means that the two species could have lived side-by-side, because they would not have directly competed for food, shelter, and territory. However, not all scientists agree that these new fossils represent a new species of hominin. Some scientists think that the fossils simply demonstrate that physical variation was great among A. afarenis.

Other World Book articles:

• Anthropology (1973-a Back in time article)
• Anthropology (1983-a Back in time article)
• Anthropology (2012-a Back in time article)

March 30, 2012

Fossilized foot bones discovered in Ethiopia show that an unknown early human relative from East Africa had apelike feet more suited for life in the trees than for walking. Anthropologist Yohannes Haile-Selassie of the Cleveland Museum of Natural History in Ohio described 3.4 million-year-old fossils in the March 28, 2012, issue of the journal Nature. The scientists concluded that the fossils are from an early hominid. (Also called hominins, hominids are the scientific family that includes human beings and early humanlike ancestors.) However, the fossils are from a foot with long digits and an opposable big toe much like those in modern apes. (An opposable digit can be placed opposite another digit, such as the human thumb to the fingers.) These feature are useful for grasping tree limbs, but they make walking upright on the ground difficult. The fossils also indicate the creature’s foot lacked a distinctive arch, a necessary feature for efficient upright walking.

These new fossils were discovered at a site called Burtele in the Afar region of northeastern Ethiopia. The site is about the same age and only a few miles from Hadar, where fossils of Australopithecus afarensis were first discovered by anthropologist Donald C. Johanson in 1974.  A. afarensis was an early humanlike creature known in part from a fossil skeleton nicknamed “Lucy.” The anatomy of Lucy and other A. afarensis fossils reveals that the creatures were small but walked upright on the ground like modern humans. Lucy’s foot anatomy shows a distinct arch and her big toe was aligned with the other four digits of the foot, the way it is in modern humans. These anatomical features allow for efficient walking on two legs on the ground. Preserved footprints at Laetoli, a site in northern Tanzania that also preserves fossil remains of A. afarensis prove that these creatures walked much the same way as modern humans do as long as 3.7 million years ago.

The skeleton of "Lucy," a prehuman ancestor that lived about 3.2 million years ago, has revealed that this australopithecine walked in much the same way as modern humans do. Lucy lived at about the same time as a newly discovered prehuman species that lived mostly in the trees. (Institute of Human Origins)

Scientists cannot assign a species name to the Burtele fossil without finding additional parts of the skeleton, such as the skull or teeth. But the fossils demonstrate that Lucy and her kind were only one of perhaps several hominid species that inhabited the forests and grasslands of East Africa more than 3 million years ago. Each species was adapted to a different habitat and likely had different anatomy and behavior, including how they moved around. As Lucy and her kind strolled along the plains, their distant cousins may have watched them pass from a perch in the trees.

Additional World Book articles:

• Evolution
• Prehistoric people
• Rethinking the Human Family Tree (a special report of historic interest)
• Anthropology 1974 (Back in Time article)
• Anthropology 1983 (Back in Time article)