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Scientists discovered Mars as the shepherd for our lost moon twin



AOP scientists discover Mars as the shepherd for our lost moon twin

Describe the planet Mars and its troop of Trojans orbiting the Lagrange L4 and L5 points. The dashed curve follows the orbit of the planet. At L5, asteroid 101429 is indicated by a blue point, asteroid Eureka and its family are indicated in red and amber. Credit: Armagh Observatory

An international team of planetary scientists led by astronomers at the AOP has found an asteroid that follows Mars in composition very similar to the moon. The asteroid can be an ancient piece of debris, resulting from the giant effects that form the moon and other rocky planets in our solar system such as Mars and Earth. The research is published in the journal Icarus, also has implications for the search for primitive objects related to our planet.


Trojans are asteroids that follow the planets in their orbits when a flock of sheep can follow a shepherd, trapped in a 60-degree gravity “safe haven” in the foreground and forward. after the planet (Figure 1). They are of great interest to scientists because they represent matter left over from the formation and early evolution of the solar system. Those several thousand trojans exist along the orbit of the giant planet Jupiter. Closer to the sun, astronomers have so far discovered only a handful of Mars Trojans, the next planet to Earth.

A team consisting of scientists from Italy, Bulgaria and the United States and led by the Armagh Observatory and the Planetarium (AOP) in Northern Ireland have been studying Mars Trojans to understand what they tell us. about the early history of the worlds inside our solar system — the so-called terrestrial planets – but also to inform Trojan searches on Earth. Ironically, it’s much easier to find Mars Trojans than on our own planet because these Earth Trojans, if they exist, are always close to the Sun in the sky, where it’s very difficult. to point the telescope in. An Earth Trojan, named 2010 TK7, was found a decade ago by NASA’s WISE space telescope, but the computer model showed it to be a temporary visitor from the asteroid belt. planet between Mars and Jupiter rather than a planetary relic from Earth formation.

To find out the composition of the Mars Trojans, the team used X-SHOOTER, a spectrophotometer mounted on the Southern European Observatory’s Very Large 8-meter Telescope (VLT) in Chile. X-SHOOTER looks at how the asteroid’s surface reflects sunlight in different colors – its reflective spectrum. By performing spectroscopic comparisons with other Solar System celestial bodies with a known composition, a process called classification, the team hopes to determine whether the asteroid was made from the object. Is it similar to rocky planets like Earth or is it a fragment of carbon- and water-rich matter typical of Jupiter’s outer solar system.

One of the Trojans that the team looked at was the asteroid (101429) 1998 VF31. The color data present on the object suggests a similar composition to a common asteroid known as conventional chondrites. The VLT’s light-collecting power allows for higher quality data collection about the asteroid than ever before. By combining these new measurements with data previously obtained at NASA’s Infrared Telescope Facility in Hawaii, the team then attempted to classify 101429. They found that the spectrum was mismatched. are suitable for any particular type of asteroid or asteroid and as a result they have expanded the analysis to include spectrum from other types of surfaces.

To their surprise, they found (Figure 2) that the spectrum was best suited not for other small objects but with our closest neighbor, the moon. As Dr. Galin Borisov, a PDRA at AOP who has been deeply involved in spectroscopic analysis explains: “Many of the spectra we have for asteroids are not very different from the moon but when you look closely. there will be important differences, for example the shape and depth of the broad spectrum absorption at 1 and 2 micrometre wavelengths. death signs for parts of the moon where exposed foundations like crater and mountain interiors. “

Where could such an unusual object come from? One possibility is that 101429 is just another asteroid, perhaps similar to conventional chondrite meteorites, acquiring its moon-like appearance through repeated exposure to solar radiation, a process is called space weathering.

In addition, the asteroid may look like the moon because it comes from the moon. Dr. Apostolos Christou, AOP astronomer and lead author of the paper explains: “The early solar system was very different from what we see today. The space between newly formed planets is filled with debris and collisions are common: Large asteroids – we call these planets planets – are constantly hitting the moon and other planets A debris from such an impact. may have reached Mars’ orbit while the planet was still forming and trapped in its Trojan clouds. “

The third scenario, and perhaps more likely, is the object coming from Mars itself. As Dr. Christou pointed out, “The shape of the 101429 spectrum tells us that it is rich in pyroxene, a mineral found in the outer or crust of planet-sized objects. Mars, Like the moon and the Earth, having been affected early in its history, one of these effects caused the giant Borealis basin, a crater as wide as the planet itself. Such giant caves could easily take 101429 en route to the planet’s Lagrangian L5 point. “Indeed, Mars origin was proposed a few years ago for the Trojan sibling of 101429, a group of Trojans are collectively referred to as the Eureka family (Figure 1). These asteroids also have an unusual composition, but while 101429 is rich in pyroxene, these Eureka asteroids are mostly olivine, a mineral found deep in the planet’s mantle.

101429 and its brethren also have something to teach us about finding Earth Trojans, if they exist. The team’s previous research has shown that solar radiation causes debris, in the form of boulders or blocks the size of city blocks, from these asteroids to slowly leak out of Trojan’s clouds. Mars. If Earth’s Trojans are anything like that of Mars, then the same mechanism that would act as a source of small asteroids near Earth would stand out for their uncommon composition.

Finding these objects could become the work of the Vera C. Rubin Observatory, which is poised to begin the most ambitious survey of the solar system to date. Rubin is expected to detect 10 times more asteroids than currently and together with the GAIA satellite that has surveyed the sky from the Earth-Sun Lagrange point L2, could provide us with The best short-term prospects for tracking fragments of the Trojan Earth Companion.


The astronomers found the orbits of the remaining Martian hosts of the ancient small planets


More information:
Apostolos A. Christou et al. Composition and origin of the L5 Trojan asteroid on Mars: Insights from the spectrum, Icarus (Year 2020). DOI: 10.1016 / j.icarus.2020.113994

Provided by Armagh Observatory

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