(10302) 1989 ML is an unnamed

near-Earth asteroid A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun (perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit aro ...

. It is relatively small, estimated to be around in diameter. An

Amor asteroid The Amor asteroids are a group of near-Earth asteroids named after the archetype object 1221 Amor . The orbital perihelion of these objects is close to, but greater than, the orbital aphelion of Earth (i.e., the objects do not cross Earth's orbit ...

, it orbits between

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

and

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

. It is an

X-type asteroid The X-group of asteroids collects together several types with similar spectra, but probably quite different compositions. Tholen classification In the Tholen classification, the X-group consists of the following types: * E-type – with high ...

, so its precise surface composition is yet unknown, though telescopic observations indicate it may be relatively enriched in

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

. It was discovered by Eleanor F. Helin and Jeff T. Alu at

Palomar Observatory The Palomar Observatory is an astronomical research observatory in the Palomar Mountains of San Diego County, California, United States. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

on 29 June 1989. 1989 ML was the former backup target for

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

's ''

Hayabusa was a robotic spacecraft developed by the Japan Aerospace Exploration Agency (JAXA) to return a sample of material from a small near-Earth asteroid named 25143 Itokawa to Earth for further analysis. ''Hayabusa'', formerly known as MUSES-C ...

'' mission, but launch delays meant that the rendezvous had to be cancelled.

Orbit

1989 ML is classified as a

near-Earth object A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun ( perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit a ...

(NEO) and an

, meaning that its orbit never crosses the

's. It has a

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longe ...

of 1.273

astronomical unit The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its m ...

s (AU), completing an orbit around the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

every 1.436 years (524.518 days). It has a moderately

elliptical orbit In astrodynamics or celestial mechanics, an elliptical orbit or eccentric orbit is an orbit with an orbital eccentricity, eccentricity of less than 1; this includes the special case of a circular orbit, with eccentricity equal to 0. Some or ...

with an

orbital eccentricity In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values be ...

of 0.137, with its distance from the Sun varying from 1.0985 AU to 1.273 AU. 1989 ML has a relatively low

orbital inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth ...

of 4.379° with respect to the

ecliptic plane The ecliptic or ecliptic plane is the orbital plane of Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. From the perspec ...

. Its proximity to Earth means that 1989 ML's orbit is strongly perturbed and chaotic; the

Lyapunov time In mathematics, the Lyapunov time is the characteristic timescale on which a dynamical system is chaotic. It is named after the Russian mathematician Aleksandr Lyapunov. It is defined as the inverse of a system's largest Lyapunov exponent. Use T ...

of its orbit is roughly 1,000 years.

Physical characteristics

In 2007, a team of astronomers led by Michael Mueller used observations from the

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003, that was deactivated when operations ended on 30 January 2020. Spitzer was the third space telescope dedicate ...

to estimate 1989 ML's physical properties. Adopting an absolute magnitude value of , Mueller et al. derived a diameter of . Analysis of 1989 ML's

lightcurve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

, or fluctuations in its observed brightness, indicate that it rotates once every 19.228 hours and has a tumbling rotation. The high amplitude of its lightcurve implies that it may be very elongated, with its longest axis being at least 2.2 times longer than its intermediate axis.

Spectrum and surface

Spectroscopic Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectrosc ...

observations conducted by Palomar Observatory in 1999 revealed that 1989 ML has a relatively flat (or neutral) spectrum. As a result, a definitive interpretation of its surface composition could not be made, though its spectrum was noted to resemble dark, impact-shocked

chondrite A chondrite is a stony (non-metallic) meteorite that has not been modified by either melting or planetary differentiation, differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar Syste ...

s. Due to its neutral spectrum, 1989 ML was classified as an Xc-type asteroid under the Bus classification scheme, suggesting that it belongs to the E-type, M-type, or P-type classifications under the

Tholen classification An asteroid spectral type is assigned to asteroids based on their reflectance spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally different ...

scheme. These asteroid types are spectrally degenerate, meaning that they can only be distinguished from each other by albedo. E-type asteroids have relatively high geometric albedos of 0.3–0.6; M-type asteroids have moderate albedos of 0.1–0.2; and P-type asteroids have dark albedos below 0.1, appearing to be rich in

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

s. Mueller et al. estimated 1989 ML's geometric albedo to be , suggesting an E-type classification and ruling out a P-type classification. 1989 ML's optical and

near-infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those of ...

colors were additionally compared to other asteroids, demonstrating that they differed from the color data of M-type and P-type asteroids. They also differed from the colors of the E-type asteroids 64 Angelina and 3103 Eger, but agreed with the color of

44 Nysa 44 Nysa is a large and very bright main-belt asteroid, and the brightest member of the Nysian asteroid family. It is classified as a rare class E asteroid and is probably the largest of this type (though 55 Pandora is only slightly smaller). ...

, another E-type asteroid. Nysa-type spectra are consistent with

silicate A silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is also used ...

mineralogy enriched in iron, whilst Angelina-type spectra are consistent with silicates containing

sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...

s, indicating that 1989 ML is relatively enriched in iron.

Exploration

1989 ML is an attractive target for

spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...

exploration due to its relative accessibility from Earth. It was considered as a backup target of

JAXA The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into o ...

's sample-return mission ''

'' (then MUSES-C), with the primary target being

4660 Nereus 4660 Nereus (Provisional designation in astronomy, provisional designation 1982 DB) is a small (about ) asteroid. It was discovered by Eleanor F. Helin on 28 February 1982, approximately a month after it passed from Earth. Nereus is potentiall ...

. However, both targets had to be given up due to launch delays. ''Hayabusa'' would instead go on to rendezvous with

25143 Itokawa 25143 Itokawa (provisional designation ) is a sub-kilometer near-Earth object of the Apollo group and also a potentially hazardous asteroid. It was discovered by the LINEAR program in 1998 and later named after Japanese rocket engineer Hideo ...

in 2005. 1989 ML was also considered by the

European Space Agency The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...

as a candidate target for the ''

Don Quijote Don, don or DON and variants may refer to: Places *Don (river), a river in European Russia * Don River (disambiguation), several other rivers with the name * Don, Benin, a town in Benin * Don, Dang, a village and hill station in Dang district, G ...

'' mission concept to study the effects of impacting a spacecraft into an asteroid; however, they too changed to other targets.

References

External links