OSIRIS-APEX: The Mission Aiming at the Infamous Apophis Asteroid

The OSIRIS-APEX mission is set to intercept the infamous Apophis asteroid during its remarkably close pass by Earth on April 13, 2029. Image Courtesy: Conceptual Image Lab, NASA’s Goddard Space Flight Center

Following the insightful OSIRIS-REx mission that increased our understanding of the potentially dangerous asteroid Bennu, NASA is transitioning the mission to focus on another potentially hazardous asteroid, Apophis.

After a seven-year voyage through space, accruing over 4 billion miles, the OSIRIS-REx mission has successfully gathered and returned the first U.S. asteroid sample from the near-Earth asteroid Bennu. However, the spacecraft’s journey is far from over.

The mission, led by the University of Arizona, has been extended by NASA, allowing the spacecraft to investigate another near-Earth asteroid, Apophis. The mission henceforth will be known as OSIRIS-APEX, an acronym for OSIRIS-APophis EXplorer, with details outlined in the Planetary Science Journal.

Dani DellaGiustina of the University of Arizona’s Lunar and Planetary Laboratory, formerly the deputy principal investigator of OSIRIS-REx, now leads OSIRIS-APEX as the principal investigator.

Dani DellaGiustina, the OSIRIS-APEX mission’s principal investigator. Image by Christopher Richards/University of Arizona

The Apophis Encounter

Shortly after releasing the collected sample back to Earth on September 24, the OSIRIS-REx spacecraft ignited its thrusters to chart a course toward Apophis, anticipating a meeting in 5.5 years, just after the asteroid’s own close Earth flyby. The trajectory includes a sequence of Earth gravity assists and several tight orbits around the sun.

By April 2, 2029, the spacecraft’s cameras will commence data collection on the asteroid’s approach. Observations of Apophis will also be conducted from Earth-bound telescopes. However, immediately following the close encounter, the asteroid will be positioned too close to the sun for optical telescopes on Earth to observe, making spacecraft observations crucial for detecting any encounter-induced changes.

On April 13, 2029, the spacecraft is due to overtake Apophis as it zips by Earth’s surface at a distance of 20,000 miles. Scientists will devote the subsequent 18 months to scrutinizing the asteroid in detail, including stirring up the surface material with the spacecraft to discover what’s hidden underneath.

Apophis’s Notoriety

“Apophis has garnered a notorious reputation,” remarks DellaGiustina, an assistant professor of planetary sciences. Initially, its discovery in 2004 was accompanied by concerns over a potential Earth impact in 2029, but those fears have been dispelled. Subsequent worries pointed to a 2036 impact, yet current analyses and models now dismiss any threat from Apophis for at least the next century. Despite this, Apophis continues to loom large in the consciousness of those in the field. Its close pass by Earth in 2029, although not an impact event, will still bring it remarkably near.

The Apophis asteroid, at 340 meters wide, is a stony S-type, composed of silicate materials and nickel-iron, distinct from the C-type carbon-rich asteroids like Bennu, OSIRIS-REx’s initial target. Apophis is believed to have been nudged towards Earth’s vicinity following a collision in the asteroid belt. It will pass within a range closer than some of Earth’s satellites and one-tenth the distance to the moon, offering the nearest approach by an asteroid of this size in recorded history, with visibility by the unaided eye in the Eastern Hemisphere. Such proximity of an asteroid this large to Earth is a rare event, happening about once every 7,500 years.

Choosing the Next Objective

The team had contemplated other potential destinations, including Venus, but selected Apophis due to its accessibility for close observation, explained DellaGiustina. The asteroid’s proximity will allow for the study of its interactions with Earth’s gravity, particularly tidal forces that may unveil the underlying materials on its surface.

“Apophis will approach so near that we expect some level of activity on its surface,” noted DellaGiustina, suggesting the possibility of landslides or particle ejections that could create a comet-like tail from the asteroid. The impending close passage constitutes a significant natural experiment.

The team speculates that Apophis may be a “rubble pile” – an aggregation of debris held together by gravity, a concept crucial for understanding planet formation. Insights into Apophis’s composition could offer valuable data for planetary defense strategies, especially since most asteroids that could pose a threat to Earth are similar S-type bodies.

Connecting Meteorites and Asteroids

“We’ve learned a great deal from Bennu, particularly about how rocky bodies behave and evolve over time,” says DellaGiustina. With samples soon to be analyzed, the mission may further link meteorites found on Earth to their parent bodies in space, aiding in a deeper understanding of our solar system’s history.

“Apophis is a significant target of interest,” she adds, emphasizing the relevance of the mission to the wider scientific community and the public. As we look to the skies in anticipation, OSIRIS-APEX is primed to illuminate the enigmatic Apophis, transforming a figure of concern into a source of profound cosmic insight.

Frequently Asked Questions (FAQs) about OSIRIS-APEX mission

More about OSIRIS-APEX mission

• NASA’s OSIRIS-APEX Mission Overview
• Planetary Science Journal – OSIRIS-APEX Mission
• University of Arizona’s Lunar and Planetary Lab
• Asteroid Apophis – Potentially Hazardous Asteroids
• NASA Goddard Space Flight Center