Asteroid 2009 DD45: A Reminder of Planetary Vulnerability to Asteroids

Asteroid 2009 DD45, trajectory near Earth — Artistic representation of **asteroid 2009 DD45** crossing Earth's orbit.
Image source: astronoo.com (new window) — AI-generated image, public domain.

Scientific summary

Astronoo's article presents a detailed analysis of asteroid 2009 DD45, an Earth-crossing asteroid from the Apollos family. The study examines its physical characteristics (size, mass, orbit) and the kinetic energy it would release upon impact with Earth. The article evaluates different impact scenarios (atmospheric, oceanic and terrestrial) and their regional consequences, comparing them to historical events like Tunguska. It highlights planetary vulnerability to these objects and the importance of surveillance programs such as those of NASA and ESA.

What would happen if asteroid 2009 DD45 struck Earth?

This article focuses on asteroid 2009 DD45, a small celestial body discovered in February 2009 that passed astonishingly close to our planet. But what would be the consequences of a hypothetical impact of this asteroid on Earth? The answer depends on several factors: its estimated size (between 30 and 40 meters in diameter), its approach velocity (about 20 km/s) and the impact location. The energy released would be equivalent to several megatons of TNT, about 70 times the Hiroshima bomb. Such an impact would produce a destructive shockwave over hundreds of kilometers in the case of an atmospheric explosion (like the Tunguska event in 1908), or a regional tsunami in the case of an ocean impact. The article explores these scenarios to show that, even for a modest asteroid, the threat is real and justifies constant astronomical monitoring.

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Planetary vulnerability to asteroid 2009 DD45

The small asteroid 2009 DD45, discovered in February 2009, belongs to the Apollo family. Its diameter is estimated between 30 and 40 meters and its mass could reach 1 × 10⁸ kg. This type of celestial body is classified as an Earth-crossing asteroid because it crosses Earth's orbit. On March 2, 2009, it passed only 63,500 km from Earth, about one-fifth of the Earth-Moon distance. The probability that an asteroid of this size strikes Earth in any given year is estimated at approximately 1 in 1000 to 1 in 5000, which remains low but not negligible over long time scales.

N.B.:
The Apollos constitute a family of Earth-crossing asteroids characterized by a semi-major axis greater than 1 AU and a perihelion less than 1.017 AU (Earth's distance from the Sun varies between 0.983 AU and 1.017 AU). This means their orbit intersects Earth's, making them potentially dangerous in the event of spatiotemporal coincidence. The Apollos include several remarkable objects such as (1862) Apollo which gave its name to the group, (4179) Toutatis, (6489) Golevka and (99942) Apophis whose close approach in 2029 is particularly studied.

Classification of Earth-crossing asteroids

NEAs (Near-Earth Asteroids) are classified into four main families according to their orbits:

Apollos: semi-major axis a >1 AU and perihelion q <1.017 AU. Their orbit crosses Earth's.
Atens: semi-major axis a <1 AU and aphelion Q>0.983 AU. Their orbit is mainly inside Earth's but crosses it.
Amors: semi-major axis a >1 AU and perihelion 1.017
Atiras (or Apoheles): orbit entirely inside Earth's (Q <0.983 AU).

This classification makes it possible to assess their potential danger to our planet and to prioritize astronomical monitoring.

Table of some remarkable Earth-crossing asteroids

Table of NEA asteroids classified by size and type
Name / Designation	Estimated diameter	Minimum approach distance	Notable passage date	NEA Type	Comment
(3200) Phaethon	5.8 km	10.4 million km	2017	Apollo	Parent body of the Geminid meteor shower
(2062) Atira	5 km	16.6 million km	2018	Atira	Asteroid with orbit entirely inside Earth's
(4179) Toutatis	2.7 km	1.55 million km	2012	Apollo	Asteroid with chaotic motion, visited by Chang'e 2 probe
(7335) 1989 JA	1.8 km	4 million km	2022	Apollo	Considered potentially hazardous by NASA
(1862) Apollo	1.45 km	1.5 million km	1983	Apollo	Discovered in 1932, gave its name to the Apollo family
(6489) Golevka	0.53 km	4.6 million km	1995	Apollo	First asteroid for which the Yarkovsky effect was measured
(101955) Bennu	500 m	300,000 km (future predictions)	2135	Apollo	Target of the OSIRIS-REx mission, long-term impact risk studied
(454100) 2013 BO73	~500 m	2.9 million km	2016	Apollo	Large Apollo monitored, orbit close to Earth's
(99942) Apophis	~370 m	31,000 km	2029	Apollo	Extremely close passage, below geostationary satellite orbit
(3361) Orpheus	~300 m	2.8 million km	1982	Apollo	Classified as potentially hazardous (PHA)
2009 DD45	30–40 m	63,500 km	2009	Apollo	Passage at only 1/5 of the Earth-Moon distance

Asteroid 2009 DD45: Kinetic energy and impact scenario

The kinetic energy of a small object ~35 m in diameter is given by the formula E = ½ m v². Assuming an average density of 3000 kg/m³ and an approach velocity of 20 km/s, the asteroid's mass is approximately 6.7 × 10⁷ kg. The energy released upon impact would reach approximately 3.2 megatons of TNT, about 70 times the energy of the Hiroshima bomb.

N.B.:
Scientists, engineers and media use this unit (megatons of TNT) to report the potential danger of an impact to decision-makers or the general public. This allows comparison of natural impact vs human energy (weapons, industrial explosions).

Atmospheric and geophysical consequences

Atmospheric explosion scenario

An atmospheric impact could cause aero-fragmentation, dispersing energy in a destructive shockwave over several hundred kilometers.

Oceanic and terrestrial scenarios

If the impact occurred at sea, a tsunami would likely be regional. On land, the shockwave and fireball would have effects comparable to a strategic nuclear weapon.

Comparative table of impact scenarios

Comparison of impact scenarios for asteroid 2009 DD45
Scenario	Main effect	Affected area	Comment
Atmospheric aero-fragmentation	Shockwave	Radius of 100 to 200 km	Comparable to Tunguska (1908)
Oceanic impact	Tsunami	Regional coasts	Amplitude of several tens of meters locally
Terrestrial impact	Craterization + shockwave	Impact zone + local atmosphere	Destruction equivalent to a major nuclear weapon

References

FAQ: Everything you need to know about asteroid 2009 DD45

What is asteroid 2009 DD45?

2009 DD45 is a small Earth-crossing asteroid from the Apollo family, discovered in February 2009. Its diameter is estimated between 30 and 40 meters and it passed only 63,500 km from Earth on March 2, 2009, about one-fifth of the Earth-Moon distance.

Why is asteroid 2009 DD45 considered potentially dangerous?

Although it is not classified as potentially hazardous (PHA) according to official criteria (size >140 m and minimum approach distance <0.05 AU), its very close passage and sufficient size to cause significant regional damage make it an object of surveillance. The energy it would release upon impact would be on the order of 3.2 megatons of TNT.

What is the probability that 2009 DD45 will strike Earth one day?

The annual probability that an asteroid of this size (30 to 40 meters) strikes Earth is estimated between 1 in 1000 and 1 in 5000. Over longer time scales (several centuries or millennia), the risk becomes more significant. However, the orbit of 2009 DD45 is relatively well known and no impact is predicted in the near future.

What would be the consequences of an impact of 2009 DD45 on Earth?

The consequences would depend on the impact location. In the case of an atmospheric explosion (aero-fragmentation), a shockwave could devastate an area of 100 to 200 km in radius (like Tunguska). In the case of an oceanic impact, a regional tsunami could form. On land, the impact would create a crater and local devastation equivalent to a major nuclear bomb.

Where can I find more information about this asteroid and near-Earth objects?

You can consult the websites of NASA's CNEOS (new window) and the ESA NEO Coordination Centre (new window). These agencies provide updated data, ephemerides and analyses on near-Earth objects.