- Next week, NASA plans to launch its Lucy probe on the Trojan asteroids that surround Jupiter.
- Trojans are like fossils, unchanged since the solar system was born 4.6 billion years ago.
- Lucy aims to visit eight different asteroids, a record number of encounters.
NASA is about to launch an ambitious mission to explore swarms of asteroids as old as our solar system.
These asteroids, called Trojans, orbit the sun alongside Jupiter. One group of them lead the gas giant along its orbital path, and another group follows it. These space rocks were formed during the birth of our solar system almost 4.6 billion years ago and have remained virtually unchanged since.
Scientists want to know what’s in these time capsules, so NASA is sending a 52-foot-wide spacecraft, called Lucy, to investigate. The probe is expected to be launched aboard an Atlas V rocket from Cape Canaveral, Fla., On October 16.
Lucy is due to visit eight asteroids over the next 12 years. One of these space rocks is in the solar system’s main asteroid belt, between Mars and Jupiter, which Lucy will pass on her way to the other seven asteroids, which are part of the Trojans.
“These objects that we consider to be the fossils of the formation of the planets,” Hal Levison, the mission’s principal investigator, said in a briefing last month.
This is where Lucy got her name – it’s a reference to the famous fossilized human ancestor 3.2 million years old. At the time of its discovery in 1974, Lucy was the oldest and most complete hominid skeleton ever discovered. She was proof that human ancestors walked upright, which has helped paleoanthropologists piece together the history of human evolution. Scientists hope that the Trojan asteroids can do the same for the outer solar system.
“Some of the most important planetary scientific questions we try to answer focus on the origin and evolution of the solar system. Asteroids and other small bodies are really important keys to understanding this story,” Lori Glaze, director of NASA’s planet of science, said in the briefing.
Lucy’s planned trip would see her visit more asteroids than any previous spacecraft. It will also venture further from the sun than any solar probe has ever been.
Liftoff is scheduled for 5:34 a.m. ET on October 16. If the weather delays the launch, NASA has another 20 days in its window.
Close encounters of the asteroid genre
Lucy’s mission has been in preparation for seven years. The original plan was to visit just two asteroids, but engineers and scientists at NASA got more ambitious when designing the spacecraft and planning its trip.
Now the probe has a record range. Some of her eight stops are two-for-one: An asteroid has its own satellite – a smaller rock trapped in its orbit – and two of Lucy’s targets are a pair of binary asteroids circling each other.
But Lucy’s encounter with each primordial space rock will be brief. The spacecraft cannot slow down or land on its targets – that would require too much thruster – so it will travel within 600 miles of their surfaces, moving at 3-5 miles per second.
During the few hours that it approaches and passes the asteroids, Lucy’s scientific instruments will collect data on their composition, density and size. He might even discover rocks or rings surrounding asteroids – features too small to be seen from Earth.
By the end of Lucy’s trip, NASA expects to have spent $ 981.1 million on the mission, according to Glaze.
Lucy must revisit Earth 3 times to reach her targets
Scientists have identified more than 7,000 Trojan asteroids, divided into three main types. One group looks like space rocks in the asteroid belt between Mars and Jupiter, while the other two look like icy objects in the Kuiper belt on the outskirts of the solar system.
This suggests that different types of Trojans were formed by different processes and in different parts of the solar system. Scientists don’t know how they got together along Jupiter’s orbit. Lucy will therefore visit the asteroids of each type to try to find out.
“Covering this diversity is essential. And finding a trajectory that will actually allow us to visit all of these types of objects has been a real chore,” said Levison.
To reach all of her destinations, in fact, Lucy has to come back to Earth three times to get a gravity boost from our planet. This will make it the first spacecraft to travel to orbit of Jupiter and return.
NASA bets on asteroids
NASA is sending probes to asteroids scattered throughout the solar system.
“Lucy is part of a collection of ambitious missions to study the diversity of these asteroid populations that will help us complete more pieces of this cosmic puzzle,” said Glaze.
NASA’s New Horizons spacecraft has been studying asteroids and other objects in the Kuiper Belt, beyond Neptune, since it flew over Pluto in 2015.
The agency’s OSIRIS-REx spacecraft, meanwhile, landed on an asteroid last year, pierced its surface and collected a rock sample. This probe is on its way back to Earth with the sample in tow. Japan recently completed a similar mission and brought its own asteroid samples to Earth. NASA and the Japanese space agency therefore plan to exchange pieces of their samples.
Other missions aim to prepare for the possibility that an asteroid could strike our planet. In November, NASA plans to launch a spacecraft to crash into a nearby asteroid. This mission, called the Double Asteroid Redirection Test (DART), tests a method that could deflect space rocks from a collision course with Earth. NASA is also working on a new space telescope, called the NEO (near-Earth object) Surveyor, which would help scientists catalog dangerous asteroids in our neighborhood.
Next year, NASA plans to launch another probe, called Psyche, at a metallic asteroid that could be the remaining core of an ancient planet.
“All of these destinations are incredibly interesting. And in each case, we are exploring places where no spacecraft has ever been, so we won’t know for sure what we will discover until we get there,” Glaze said. “But we know that whatever Lucy finds will give us vital clues as to how our solar system was formed.”