The UN's Planetary Defender: Aarti Holla-Maini's Critical Role in Global Security
Aarti Holla-Maini, a British lawyer with extensive experience in the satellite industry, holds one of the most unique and critical positions within the United Nations system. As the director of the UN's Office for Outer Space Affairs (Unoosa), she serves as the designated official who would alert the UN secretary general if a significantly large asteroid were detected on a potential collision course with Earth. This responsibility, which she humorously refers to as "Armageddon" duty, became startlingly real just over a year ago.
The Real-Life Asteroid Alert That Tested Global Preparedness
In late December 2024, a robotic telescope in Chile detected a distant space rock initially estimated to be the size of a small building. While asteroid sightings are common, this particular object—emotionlessly named 2024 YR4—presented a growing concern as observations continued. Over the following three weeks, its Earth impact probability gradually increased from less than 0.05% to more than 1% for a potential impact in 2032.
"This wasn't a simulation or a drill," Holla-Maini recalls. "It was real." The asteroid's size and speed meant that an impact could release energy comparable to hundreds of times the power of the Hiroshima bomb, potentially wiping out an entire city or region. Although the chance remained minuscule—essentially a 99% likelihood of missing Earth—the threat met Unoosa's criteria for issuing its first global notification since the UN established its planetary defense collaboration in 2013.
Activating the International Response Mechanism
Romana Kofler, a Unoosa programme officer who serves as the point of contact for planetary defense, had been working late into the night coordinating with the International Asteroid Warning Network. This UN-backed body includes astronomers, NASA and European Space Agency (ESA) members, and experts specializing in calculating the orbits and trajectories of distant space objects.
"We had trained for this with simulations, but this was the real thing," says Kofler. "The adrenaline kicked in." After alerting Holla-Maini, they quickly drafted and sent a formal notification to UN Secretary General António Guterres, who would disseminate the information to all 193 member states. "We were very quick in preparing the drafts," Holla-Maini notes. "So this was the first real-time test of an international response."
The Growing Reality of Space Threats
The threat from objects in outer space is far from theoretical. In 2013, a meteor measuring approximately 20 meters (60 feet) wide exploded over Chelyabinsk, Russia, releasing energy equivalent to 500 kilotonnes of TNT. The resulting shock wave shattered windows in thousands of apartment blocks, injuring more than 1,200 people with flying glass and debris. The fireball glowed 30 times brighter than the sun, causing immediate skin burns and demonstrating that even smaller space rocks can inflict mass casualties without warning.
For a brief period last year, 2024 YR4 represented the most significant near-term threat since the discovery of asteroid Apophis in 2004. On the Torino Impact Hazard Scale—which ranges from zero (no risk) to 10 (certain collision threatening civilization)—2024 YR4 reached level three. This activation triggered another UN-endorsed body, the Space Mission Planning Advisory Group, tasked with developing potential Earth-saving measures including asteroid deflection techniques similar to those tested in NASA's successful 2022 Dart mission.
Beyond Asteroids: Unoosa's Expanding Responsibilities
Pronounced "Younoosa," the Office for Outer Space Affairs operates from the modest Vienna International Centre with just 35 employees. Established in the late 1950s during the dawn of the space age, the agency was created with the intention of preventing Earth's political rivalries from extending into space. Today, its small team manages an increasingly critical portfolio as governments and businesses expand their operations beyond our atmosphere.
Holla-Maini, who transitioned from 25 years in the commercial sector to the UN's sprawling bureaucracy, now spends much of her time traveling globally to conferences while promoting international law and regulation in an increasingly crowded and competitive space environment. The agency runs multiple programmes including Space for All, which helps non-space-faring nations access orbital benefits, and UN-Spider, which facilitates satellite imagery access for countries facing natural disasters.
The Critical Role of Satellite Registration and Collision Prevention
Perhaps Unoosa's most vital function has become its role as the official register of satellites launched into Earth's orbit. With the number of active satellites exceeding 10,000 and many times more planned for launch, the space nearest Earth has transformed into a congested and risky traffic zone. The agency has consequently evolved into an informal "hotline" for potential satellite collisions—a role that becomes diplomatically complex when the satellites belong to nations with no formal relations.
Holla-Maini recounts a tense incident in June 2024 when the Malaysian Space Agency contacted Unoosa on a weekend after one of its non-manoeuvrable satellites appeared to be on a collision path with a North Korean satellite, with just 75 meters separating them. With no direct communication line to Pyongyang, Holla-Maini's team sent information to every known North Korean email address without expectation of response. Remarkably, the North Korean satellite moved out of the way without any bilateral conversation.
A Small Team with Global Impact
Whether sounding the alarm about potentially destructive asteroids, facilitating disaster relief imagery for floods in Morocco, or preventing catastrophic collisions in Earth's orbit, Holla-Maini emphasizes that her "tiny team" in Vienna punches well above its weight. "Because we have been in this straitjacket of not enough staff, not enough budget, it has forced the office to be extremely efficient," she explains.
The 2024 YR4 asteroid scare ultimately served as a valuable test for Unoosa's planetary defense capabilities. Although the asteroid's impact probability peaked at more than 3% in February 2025, it has since dropped to negligible levels. "All of a sudden," Holla-Maini reflects, "it was gone." Yet the experience reinforced the importance of her office's work in protecting our planet from threats both near and far.
