The study of near-Earth asteroids (NEAs) is driven by both scientific and practical reasons. Because of their proximity to our planet, they can provide key information regarding the delivery of water and organic-rich material to the early Earth, and subsequent life-threatening emergencies. On the other hand, these small bodies of the solar system have non-negligible long-term probabilities of colliding with the Earth, and can be targets of future space exploration.
In the framework of the EURONEAR collaboration, a group of astronomers performed a spectroscopic survey of NEAs using the Isaac Newton Telescope (INT) equipped with the Intermediate Dispersion Spectrograph (IDS). The ING studentship program, aimed at providing hands-on training to 4-6 students per year, was at the core of this research. The students were invited to take part in the EURONEAR survey by conducting observations, and they were assisted remotely by the Astronomical Institute in Bucharest (Romania) by one of the program's principal investigators.
The purpose of this collaborative work was to spectroscopically characterize a significant sample of NEAs with sizes in the range of 0.25-5.5 km (categorized as large). The sizes of the asteroids are determined by their absolute magnitudes (the absolute magnitudes of the observed objects are shown in Figure 1) and by their surface properties (albedos), which can be inferred from spectroscopy.
The team of astronomers found that the NEAs population shows a large variety of objects in terms of physical and dynamic properties. Broadly, it matches the composition patterns of the inner main asteroid belt (located at heliocentric distance between 2.2 and 2.5 astronomical units), which is the likely source region of these bodies. However, they show spectral differences because NEAs are subject to planetary approaches, energetic micrometeorite bombardment, strong solar wind and radiation effects.
First, the asteroids with a carbonaceous-like composition, denoted as C-complex, have a higher value of heliocentric perihelion distance (in the order of one astronomical unit) than the median perihelion of bodies dominated by olivine and pyroxenes minerals.
These C-complex asteroids break up more easily as a result of thermal effects and the smaller ones are more likely to be destroyed farther from the Sun. And secondly, this work outlines evidence that thermal fat fragmentation is one of the major processes for rejuvenation of NEA surfaces.
One extreme case corresponds to (267223) 2001 DQ8 which has a surface temperature at perihelion (at a heliocentric distance of 0.18 astronomical unit) of about 625 K, but when it reaches aphelion at 3.5 astronomical units from the Sun, the temperature drops to 150 K. This large temperature variation leads to thermal fatigue followed by thermal fragmentation.
Motivated by space exploration reasons, this team of astronomers observed 31 possible targets for space missions. They included the asteroids (459872) 2014 EK24, (436724) 2011 UW158, and (67367) 2000 LY27, which are suitable for sample return exploration.
In particular, the most interesting of these is the A-type asteroid (67367) 2000 LY27. It has an olivine rich composition that may have formed in the mantle of a large body. Thus, it may represent a good opportunity to study fragments coming from planetesimals that are differentiated (a process defined as the separation of distinct layers forming an iron nucleus, a silicate mantle and a basaltic crust) in the early history of the solar system.
Finally, 27 asteroids that are potentially hazardous (these celestial bodies show a long-term risk of colliding with our planet) were characterized. The mitigation strategy depends very much on their physical properties, so spectral data were obtained to determine their compositions.
Research Report: "Near-Earth Asteroids Spectroscopic Survey at Isaac Newton Telescope,"
Isaac Newton Group Of Telescopes
Asteroid and Comet Mission News, Science and Technology
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Scientist helps discover how water is regenerated on asteroids
Perth, Australia (SPX) Oct 09, 2019
Scientists have discovered how water molecules can regenerate on asteroids moving through space, in an exciting breakthrough that could extend to other bodies such as the Moon.
Published in the journal Nature Astronomy, new research shows water can be replenished on the surface of asteroids if both solar wind and impacting meteoroids come together at very low temperatures.
Lead Australian author Dr. Katarina Miljkovic, from Curtin University's Space Science and Technology Center, … read more