Visualizing Asteroid Data

My deeper exploration of bringing in geospatial data into planetarium software coincided with the release of Dawn’s high resolution maps from Vesta, and as I worked with my colleagues to develop a variety of educational programs on asteroid missions and research, developing an accurate depiction of Vesta in simulation software to bring these results to the public.

In 2014 Dr. Brian Day of NASA Ames, who I had worked with for a lecture on NASA’s LORRI Lunar Orbiter mission, approached me about working together to share the data from Dawn, and other high-resolution planetary mapping missions such as MESSENGER at Mercury and the Mars Reconnaissance Orbiter at Mars with other planetary geologists at the American Geophysical Union conference. Together, with collaborations from NASA JPL and the American Museum of Natural History, we hosted a “dome night” at AGU’s Winter Meeting in San Francisco, where I piloted though simulation software while Brian toured the audience over the incredible geology we were discovering on these worlds.

That same year, I had the opportunity to work with Dr. Franck Marchis of the SETI Institute to visualize his asteroid research. In particular, I created visuals for a lecture he presented on binary asteroids. We first discovered asteroids could have moons when the Galileo mission flew by the asteroid Ida in 1993, photographing its small moon, Dactyl.

Since then we’ve discovered hundreds of asteroids that exist as complex systems: some with a major body and tiny moons, like the largest Trojan asteroid, Hektor.

Others are pairs of similarly sized bodies co-orbiting, like Patroclus and its companion Menoetius–which are now the final targets for the Lucy asteroid mission–which when then discussed only as a future proposal.

While most asteroids are too small to see their shape from Earth, in some cases we have been able to bounce radar off of them during close passes to infer their rough shape. Marchis and colleagues were able to do even better. Setting up multiple observations of the asteroid Antiope in 2007 and 2008 they were able to observe the system from multiple locations as it passed in front of background stars. These observations provided just enough information to infer the silhouette of the asteroid pair, including a missing chunk of material on one of the components.

Working from these observations, Marchis had me produce a 3D visualization of that asteroid system.

Since the Apollo missions first returned lunar rock samples to the Earth, space agencies around the world have sought to retrieve such samples from more bodies of the Solar System to enhance our understanding of geologic origins of various bodies, and what, if anything, made the Earth the unique abode of life.

The Japanese Space Agency’s (JAXA) Hayabusa mission in the late 2000s caught the attention of many of my colleagues, especially as it revealed in detail the “rubble pile” structure of its small target asteroid, Itokawa.

Subsequent missions provided fresh, evolving opportunities to visualize these ambitious missions, particularly NASA’s OSIRIS-REx mission to Near Earth Asteroid Bennu.

These missions, and future sample returns, will continue to explore the geochemical similarities and differences of the many bodies in our Solar System, and what clues asteroids hold to the unique status of the Earth. Early samples reveal complex organic molecules and elemental abundances similar to Earth.

Asteroids are interesting because in many ways they are time capsules of the early solar system. Earth’s geology has been reshaped by billions of years of plate tectonics, atmospheric weathering, and interactions with the chemical processes of life. Many asteroids, however, are still representative of the raw materials of the early solar system–although they have collided with and battered each other, they haven’t experienced the chemical reformation that terrestrial rocks have.

We now understand that the planets were built out of the collisions of asteroids like these billions of years ago, and the remaining asteroids are mostly objects that failed to coalesce into the planets, locked in reservoirs around the Solar System that are protected from collision with the planets.

Populations like the Main Asteroid Belt, Jupiter’s Trojan asteroid fields, and the Plutinos beyond Neptune all represent locations in the Solar System where a balance exists between the gravity of the Sun and planets, preserving large volumes of asteroids in orbits that delicately dodge each other, preserving these relics. Realtime simulation software now allows us to visualize the motions of tens or hundreds of thousands of asteroids simultaneously, allowing us to see the complex motions that keep these objects (mostly) safe from collision with the planets.

We can partly study asteroids’ geochemistry from afar by looking at the shape of their spectrum in infrared light. This allows us to divide up the asteroids into populations based on their composition. At the most basic level we are familiar with those made mostly of rock and those made mostly of metals, but more detail reveals other differences and relationships among these bodies.

One population of particular interest are the D-type asteroids. These asteroids are often described as having a more “reddish” spectrum. Scattered around the inner Solar System, their spectrum is similar to that of the dwarf planet Pluto and other objects beyond Neptune.

D-types appear to have high concentrations of organic molecules and volatile ices. The migration of the outer planets early in the Solar System’s history may have served an important role in disrupting the outer asteroid reservoir of the Kuiper Belt, now beyond the orbit of Neptune, and sending D-types into the inner Solar System billions of years ago. The possible role of these asteroids in our cosmic origins are exactly why the Lucy mission took its name after the famous Lucy “missing link” fossil of our pre-human ancestor.

We have much to learn from asteroids, but researching them is not just theoretical. Although most asteroids are gravitationally corralled by the planets, thousands exist on trajectories that still have potential to intersect with the planets, especially through complex interactions with other asteroids and planets. This leads to occasional collision between asteroids and the planets, and given the high relative speed of objects in space, even a small asteroid can cause devastating destruction.

The cratered face of the Moon reveals a history of impacts, mostly from the first billion years of our Solar System’s history–but since it was proven in the mid-20th century that asteroids are the source of some crater features on Earth we’ve determined that our planet is covered with the pockmarks of ancient impacts. In the 1990s researchers associated one of these impact sites as a probable cause of the extinction of the dinosaurs.

On February 15, 2013 we were viscerally reminded of the threat asteroids can pose to the Earth. Astronomers were preparing for the close flyby of a small Near Earth Asteroi Duende (then designated as 2012 DA14), which slipped between Earth and the Moon on an unprecedented close flyby.

As it did, another asteroid approached from the direction of the Sun, its orbit intersected with the Earth, and it entered the atmosphere over the Russian city of Chelyabinsk. The small rocky asteroid exploded as it heated up as it rammed through the atmosphere, creating a shockwave that shattered windows across the city, with many videos of the event captured on car dashcams.

NASA had been mandated since the 1990s to discover all of the so called “planet killer” asteroids, 1 kilometer in length or bigger, and the decreasing frequency of discoveries suggest a great many of them have been found. But the Chelyabinsk impactor was likely only 20 meters across. Even small bodies can cause citywide, nationwide, or continentwide destruction and create social, humanitarian, and economic impacts that will be felt across the globe.

Scientists continue to explore planetary defense solutions to detect and protect the Earth from such asteroids. In the early 2020s the DART mission successfully tested the ability to change an asteroid orbit with a small impactor. Even slight changes to an asteroid’s orbit years in the future can safely shift them away from impact with Earth.

But the most important step of protecting the Earth is identifying the threats–that means discovering asteroids. I’ve been privileged throughout my career to work on visualizing asteroid data with the B612 Foundation, founded by astronauts Ed Lu and Rusty Schweikart, whose orbital experiences showed them just how fragile our world truly looks from space. Inspired by this, B612 advocates for planetary defense, and in recent years helped develop their ADAM application for asteroid detection, which can comb through images observatories around the world have already taken of the sky and identify undiscovered asteroids within the data and reconstruct their orbits.

The Vera Rubin Observatory in Chile is also expected to revolutionize asteroid discovery–taking high resolution images across the sky every night. This observatory has already discovered thousands of asteroids and will provide an unprecedented perspective on the true density of small asteroids that may pose a risk to the Earth.

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