NASA will soon send a space probe to Jupiter’s Trojans

The probe will examine a record-breaking number of asteroids and visit the Trojans for the first time.

In 1974, researchers in Ethiopia came across the remains of an unknown hominin. The paleoanthropologists lovingly christened her “Lucy.” And now, nearly fifty years later, a space probe of the same name is heading for Jupiter’s Trojans. It is hoped that the probe, named after the Ethiopian Lucy, can provide more insight into the formation and evolution of our solar system. And thus in a sense follows in the footsteps of its namesake, which in turn has given us greater insight into our own evolutionary history.

October 16

This new space mission has been working on for years and soon Lucy will really take to the skies; the launch is currently scheduled for October 16. So it’s high time to take a closer look at this mission – which is full of the firsts.

Lucy’s mission revolves around the Trojans. These are actually debris dating back to the early days of the solar system and collected in two swarms in Jupiter’s orbit. One swarm travels ahead of Jupiter. The other travels after Jupiter. In total, more than 9800 of these Trojans are known to us. And Lucy can’t visit them all, of course. That is why the American space agency has fished out a number of interesting specimens:

Eurybates and Queta

For example, a flyby through Eurybates and Queta is planned in August 2027. Eurybates is a 40-mile asteroid that is, in a sense, quite rare. It is a C-type asteroid and they make up only 7 percent of the Trojans. Gliding past Eurybates, Lucy actually kills two birds with one stone. In 2020, astronomers discovered that the large asteroid has a small moon. Lucy will skim right past it to get a direct look at a very small Trojan.

Polymele

In September 2027, Polymele will wait. This asteroid is 24 kilometers in size. And observations from Earth suggest it revolves around its own axis in 6.1 hours. Polymele is a slightly different type of asteroid than Eurybates; Polymele belongs to the so-called P-type asteroids.

leucus

In April 2028, Lucy will skim past a D-type asteroid: Leucus. This space rock is special because it takes 440 hours to complete a circle around its own axis. In addition, the shape is also striking; Leucus has a long axis of 31 kilometers and a short axis of 15 kilometers and is therefore very oval-shaped.

Orus

In the autumn of 2028 Lucy will also visit Orus. This is also a D-type asteroid. With a diameter of 62 kilometers, the space rock is about the same size as Eurybates. But the history of Orus is probably very different. Eurybates shares its orbit with a large number of relatives who – after all kinds of collisions – all seem to have detached from one much larger asteroid. Orus is not associated with such a family.

Patroclus and Menoutius

In 2033 Lucy also skims past Patroclus and Menoutius. The two are both about 100 kilometers in size and they orbit around the same point in space. Such binary asteroids are quite rare among Trojans.

Lucy’s journey. Image: Southwest Research Institute.

The skims past the Trojans will yield a wealth of information. Not least because no mission to the Trojans has ever been undertaken. So there is still much to discover!

Research

Lucy will, among other things, investigate the shape of the Trojans and the extent to which they reflect sunlight. The probe will also determine how many craters there are on the Trojans and how they are distributed over the surface. The distribution of minerals, ice and (complex) organic molecules on the surface of the Trojans is also discussed. Just like their composition and the properties of their surface. Finally, Lucy will also hunt for any moons or ring systems around Trojans.

It is hoped that the mission will not only reveal more about the Trojans, but also provide more insight into the evolution of our solar system. The Trojans are seen as ‘planetary cliques’: residual materials, left over after the ‘construction’ of the planets. And unlike the planets, these raw materials have hardly changed since the planets were formed. They can therefore give us a unique insight into the circumstances at the time of the formation of the planets and the materials that were available for the construction of the planets. And finally, because of their diversity, the Trojans may also reveal how those newly formed planets moved from their birthplaces. For the fact that the Trojans are so diverse indicates that they originated in different parts of the solar system, and researchers believe that they were collected during the migration of the gas giants in their current orbit and become trapped.

Lucy’s mission is very special for several reasons. Not only is the Trojans visited for the first time; it is also the first time that a spacecraft has visited so many asteroids in one mission. A total of no less than eight space stones! In addition to the seven Trojans, Lucy will also skim past asteroid Donaldjohanson (named after the discoverer of the African Lucy) in 2025. The fly-by should be seen as a dress rehearsal that precedes the fly-by of the Trojans.

With a mission duration of 12 years, we can indulge ourselves in the coming years; We will regularly be treated to new facts about these space stones that have remained underexposed until now. And of course we hope for beautiful images; Lucy is equipped with a camera that can immortalize the Trojans – despite being extremely dark – in quite detail. From about 1000 kilometers away, the camera should still be able to spot craters with a diameter of 70 meters. The images will radically change our view of the Trojans – which we now only know as pixels of light. And en passant thus also supplementing and where necessary correcting our picture of the evolution of our solar system.