Asteroid Apophis to Pass Closer to Earth Than Satellites in 2029, NASA Says

On the evening of April 13, 2029, more than two billion people across Africa, Europe, and western Asia will be able to look up and watch a faint star-like point of light drift across the sky at 42 degrees per hour [1]. That point of light will be asteroid 99942 Apophis — a 370-meter chunk of rock and metal passing just 31,600 kilometers above Earth's surface [2]. For context, the International Space Station orbits at roughly 400 kilometers, and the belt of geostationary communications and weather satellites sits at about 35,786 kilometers [2]. Apophis will thread between them.

No asteroid this large has ever been observed passing this close to Earth in recorded history. The encounter represents both a scientific windfall and an uncomfortable reminder: the infrastructure for detecting, tracking, and — if necessary — deflecting such objects remains incomplete.

From Panic to Precision: How Apophis Went From Threat to Opportunity

Apophis was discovered on June 19, 2004, by astronomers Roy Tucker, David Tholen, and Fabrizio Bernardi at the Kitt Peak National Observatory in Arizona [3]. Initial observations were alarming. By December 27, 2004, the asteroid had been assigned a 2.7% probability of striking Earth on April 13, 2029 — the highest impact probability ever recorded for a known asteroid [3]. It reached Level 4 on the Torino scale, a hazard index that ranges from 0 (no risk) to 10 (certain catastrophic collision) [4].

The panic was short-lived. Within 48 hours, additional tracking data reduced the probability sharply. By early 2005, the 2029 impact scenario had been eliminated entirely [4]. But Apophis was not done generating concern. The close flyby in 2029 could alter the asteroid's orbit enough that, if it passed through a narrow corridor of space called a "gravitational keyhole" — roughly 600 meters wide — it would be redirected onto a collision course for a return in 2036 [5].

Source: NASA/JPL Sentry

Data as of May 1, 2026CSV

Goldstone radar observations in January 2013 effectively eliminated the 2036 scenario, pushing the impact probability below one in a million [6]. A smaller but persistent risk remained for 2068, driven largely by uncertainties in the Yarkovsky effect — a subtle force caused by the uneven thermal radiation from a rotating asteroid's surface that gradually nudges its orbit [7]. In March 2021, radar observations from Goldstone and the Green Bank Observatory provided enough precision to rule out any Earth impact for at least 100 years [8].

How Close Is Too Close?

At closest approach — 21:46 UTC on April 13, 2029 — Apophis will be approximately 31,600 kilometers from Earth's surface, or about 37,600 kilometers from Earth's center (roughly 5.94 Earth radii) [2][9]. This places it well inside the geostationary satellite belt at 35,786 kilometers.

The question of whether any operational satellites face collision or gravitational perturbation risk has been assessed by space agencies and satellite operators. Apophis's trajectory geometry places it on a path that does not cross any known major satellite positions, and its gravitational influence — while strong enough to be measurable by sensitive instruments — is far too weak to perturb satellite orbits at the distances involved [9]. The asteroid's mass (estimated at 4.4 to 6.2 × 10^10 kilograms) produces a gravitational field negligible compared to Earth's at those distances [10].

The flyby will, however, dramatically alter Apophis itself. Earth's gravity will reclassify its orbit from an Aten-class (semi-major axis less than 1 AU, mostly inside Earth's orbit) to an Apollo-class (semi-major axis greater than 1 AU, crossing Earth's orbit from outside) [9]. The encounter may also trigger surface changes — landslides, reshaping — that scientists are eager to observe firsthand.

What If It Did Hit?

Though the 2029 impact has been definitively ruled out, the hypothetical consequences remain instructive. Apophis is approximately 370 meters in diameter with a mass of roughly 50 billion kilograms [10]. At its expected approach velocity, a ground impact would release energy on the order of 1,200 megatons of TNT [11].

For comparison, the 2013 Chelyabinsk event in Russia — where an approximately 18-meter asteroid exploded in the atmosphere, injuring over 1,500 people — released roughly 500 kilotons, or 0.5 megatons [12]. An Apophis-scale impact would be approximately 2,400 times more powerful. The Chelyabinsk object was roughly 50 times smaller in diameter; the energy scales dramatically with size because mass increases with the cube of diameter.

A land impact from Apophis would excavate a crater 2 to 4 kilometers across and up to half a kilometer deep [10]. If the impact corridor during the hypothetical 2029 scenario had been run through population models, the ground track would have crossed the Atlantic, parts of Central America, and the Pacific [3]. Depending on the exact impact point, millions of people could have been in the damage zone. An ocean impact would generate tsunamis affecting coastlines across multiple continents.

Two Spacecraft, One Flyby: The Science Missions

Two spacecraft are being prepared to rendezvous with Apophis during the 2029 encounter.

OSIRIS-APEX (formerly OSIRIS-REx, the spacecraft that successfully returned samples from asteroid Bennu in 2023) has been redirected by NASA to reach Apophis shortly after the close approach [13]. The mission will study how Earth's gravitational tidal forces physically alter the asteroid's surface and rotation. OSIRIS-APEX faced budget uncertainty — a last-minute $20 million allocation in a House spending bill kept the mission operational [14]. Total mission costs remain modest compared to the original OSIRIS-REx program.

Ramses, a joint ESA-JAXA mission, is designed to arrive at Apophis in February 2029 — two months before the flyby — to observe the asteroid before, during, and after the encounter [15]. ESA has awarded contracts totaling approximately €150 million ($162 million) to OHB Italia, with launch planned for April 2028 [16]. The partnership with Japan's space agency was formalized to share instrumentation and data.

For comparison, NASA's DART mission — which successfully deflected the orbit of asteroid Dimorphos in September 2022 — cost approximately $330 million and demonstrated that kinetic impact could alter an asteroid's trajectory [17]. DART exceeded expectations: the collision shortened Dimorphos's orbital period by 32 minutes, far surpassing the minimum success threshold of 73 seconds [18]. The combined Apophis observation budget (roughly $180-200 million across both missions) is less than the cost of the single DART impactor.

The Keyhole Problem: Why 2029 Makes Future Predictions Harder

The mainstream narrative frames the 2029 flyby as a resolved threat turned science opportunity. This is accurate but incomplete.

The close encounter will fundamentally scramble Apophis's orbit. Before the flyby, the uncertainty in its approach distance has been narrowed to approximately ±3.3 kilometers at 3-sigma confidence [19]. After the flyby, that precision evaporates. The exceptionally small flyby distance amplifies tiny uncertainties in the asteroid's pre-encounter trajectory into large uncertainties in the post-encounter orbit — a phenomenon physicists call "scattering" [19][7].

The gravitational keyhole concern — the roughly 600-meter-wide region of space that, if transited, would set up a resonant return impact in 2036 — has been ruled out with high confidence [5]. But the broader question persists: after 2029, the Yarkovsky effect on Apophis will change because its average distance from the Sun will increase and its spin state may be altered by tidal forces [7]. These new thermal dynamics cannot be accurately modeled until the OSIRIS-APEX and Ramses missions provide post-flyby measurements [19].

In practical terms, astronomers are confident that no impact is possible for at least 100 years [8]. But "at least 100 years" is a statement bounded by current observational precision, not a permanent guarantee. The 2029 flyby is simultaneously the event that eliminates near-term risk and the event that resets the clock on long-term orbital prediction.

The Detection Gap: 14,000 Missing Asteroids

Apophis is one asteroid. The broader problem is how many more like it remain undiscovered.

NASA's acting Planetary Defense Officer, Dr. Kelly Fast, stated in February 2026 that approximately 15,000 near-Earth asteroids larger than 140 meters remain undetected out of an estimated 25,000 total [20]. Only about 44% of the estimated population has been catalogued [21]. These mid-sized objects — capable of city-scale or regional destruction — are difficult to detect because many travel on eccentric orbits, hide in the Sun's glare, or have dark surfaces that reflect little visible light [20].

Source: NASA CNEOS / Planetary Society

Data as of Mar 1, 2026CSV

The U.S. Congress mandated in 2005 that NASA achieve 90% detection completeness for near-Earth objects above 140 meters by 2020 [21]. That deadline has been missed by over six years. The primary solution is the NEO Surveyor space telescope, an infrared instrument designed to detect asteroids by their heat emissions rather than reflected sunlight. NEO Surveyor is scheduled for launch in September 2027 aboard a SpaceX Falcon 9 [21]. Its cost has grown from an initial projection of $600 million to a confirmed $1.2 billion, largely due to schedule delays caused by earlier budget constraints [21].

If NEO Surveyor launches on schedule, it is expected to reach the 90% completeness goal within approximately 10 years of operation — roughly 2037, some 17 years behind the congressional deadline [21].

The Budget Question: Is $200 Million a Year Enough?

Source: The Planetary Society

Data as of Jan 1, 2026CSV

NASA's Planetary Defense Coordination Office budget has grown from approximately $5.8 million in fiscal year 2010 to roughly $200 million in fiscal year 2024 — a more than 30-fold increase [22]. Even at that level, it represents about 0.7% of NASA's total budget [22].

Critics of planetary defense spending argue that the per-death cost is disproportionately high compared to other risks. Asteroid impacts kill, on average, roughly 100 people per year when averaged across centuries — a figure that is "trivial in the general scheme of things," according to a 2010 National Research Council report [23]. At $200 million per year, the implied cost per statistical life saved is far higher than spending on infectious disease prevention, road safety, or climate adaptation.

Defenders of the budget offer two rebuttals. First, the average obscures the distribution: asteroid impacts follow a power-law risk profile where long quiet periods are punctuated by rare events of extreme consequence. A single large impact could kill millions or, at the extreme end, threaten civilization itself. Second, the cost of an optimal asteroid search and deflection program — estimated at roughly $100 million per year by the National Academy of Sciences — is vanishingly small relative to the value of the assets protected: every person and every piece of infrastructure on the planet [23].

The Planetary Society has argued that even after a 4,200% budget increase over 10 years, the spending level remains far below what would be considered adequate insurance against a low-probability, high-consequence event [22]. The DART mission's $330 million price tag demonstrated that actual deflection capability is affordable within NASA's existing budget — but only if detection provides enough warning time [17].

No Treaty, No Rulebook: The International Governance Vacuum

If a threatening asteroid were discovered tomorrow, no binding international treaty governs the decision to deflect it.

The current framework consists of two UN-endorsed bodies established following recommendations from the UN Committee on the Peaceful Uses of Outer Space (COPUOS) in 2013 [24]. The International Asteroid Warning Network (IAWN) coordinates detection and tracking across national observatories. The Space Mission Planning Advisory Group (SMPAG) develops recommendations for deflection and mitigation options [24].

Neither body has authority to order a deflection mission. No nation holds formal veto power, but in practice, only the United States, Europe (through ESA), China, Russia, and Japan possess the launch capability to mount a deflection attempt. Any mission would require political consensus among spacefaring nations — a process with no established timeline or decision protocol [25].

The liability question is even thornier. Under the 1967 Outer Space Treaty, a state bears absolute liability for damage caused on Earth by space objects it launches [25]. If a deflection mission altered an asteroid's trajectory but failed to prevent impact entirely — redirecting debris onto a country that would not otherwise have been struck — the launching state could face legal claims with no clear precedent for resolution. SMPAG established an ad-hoc working group on legal issues in 2016, but no binding agreements have emerged [25].

The absence of a governance framework is not merely academic. The 2029 flyby will generate unprecedented public attention to asteroid risk. Whether that attention translates into institutional preparation or fades after the asteroid passes will depend on choices made in the next three years.

What April 13, 2029 Will Actually Look Like

At peak brightness, Apophis will reach apparent magnitude 3.1 — comparable to the stars in the Big Dipper and visible to the naked eye under clear skies [1]. It will appear to move perceptibly against the background stars, crossing roughly 42 degrees of sky per hour [1]. Observers in Europe, Africa, and western Asia will have the best views.

For the scientific community, the flyby offers measurements that cannot be obtained any other way. Watching Earth's gravity physically reshape a passing asteroid — potentially triggering surface avalanches and altering its spin — has never been observed directly [15]. The data collected by OSIRIS-APEX and Ramses will calibrate models used for every future asteroid encounter assessment.

For planetary defense planners, the flyby is a deadline. The infrastructure for detection, characterization, deflection, and international coordination has been built piecemeal over two decades. Apophis's 2029 passage will test whether that infrastructure is adequate — not because Apophis itself poses a threat, but because it demonstrates how close a large asteroid can come with less than 25 years of advance warning, and how much of the response framework remains unfinished.