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A microscopic image of a metal sphere that a team of scientists argue came from an interstellar object<\/p>\n
Interstellar Expedition<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
Tiny metal spheres found on the seafloor may have come from an interstellar meteor. The researchers that recovered the spherules say their compositions don\u2019t match anything ever seen before on Earth \u2013 but it\u2019s a controversial claim.<\/p>\n
Earlier this year, Avi Loeb at Harvard University took a team on an expedition off the coast of Papua New Guinea, where models predicted that remnants of an object nicknamed IM1 would have landed. IM1 fell to Earth in 2014. Loeb and his colleagues later identified it as a possible interstellar object based on its recorded velocity, which they claim was fast enough to indicate that it hurtled to Earth from beyond our solar system. They hoped to locate its remains on the ocean floor.<\/p>\n
During the expedition, the researchers found about 700 tiny iron-rich spherules. They have started analysing the compositions of those spherules. Of the 57 they\u2019ve examined so far, five seem to have unusual compositions.<\/p>\n
<\/p>\n These five orbs are particularly rich in the elements beryllium, lanthanum, and uranium, so the researchers have dubbed them BeLaU spherules. The spherules also have particularly low concentrations of elements that scientists would expect to evaporate in the extreme heat a meteor generates as it passes through Earth\u2019s atmosphere, indicating that they came from space. But their compositions aren\u2019t consistent with origins on Earth, the moon or Mars, Loeb says.<\/p>\n \u201cUsually when you have spherules that originated from meteors in the solar system, their abundances deviate by, at most, an order of magnitude\u201d he says. These deviate by up to a factor of 1000. \u201cIf you combine everything that we know\u2026 I\u2019m pretty confident that these came from an interstellar object.\u201d<\/p>\n Loeb says these compositions indicate that the spherules probably came from a differentiated object, one that\u2019s had enough time for the densest elements to sink to the middle. But to some other researchers, that doesn\u2019t track. \u201cThese interstellar objects, we expect them to be leakage from the Oort cloud equivalents around other stars\u2026 not these differentiated objects that he\u2019s suggesting,\u201d says Alan Rubin at the University of California, Los Angeles. \u201cThey\u2019re not what you would expect from interplanetary material.\u201d<\/p>\n Even the idea that these spherules are different from rocks we\u2019ve already found is controversial. \u201cHe\u2019d have to compare them to every rock type on Earth and every mineral composition, and then do the same to every mineral and rock from meteorites,\u201d says Matthew Genge at Imperial College. \u201cEven if this mammoth task resulted in a lack of matches, then it still isn\u2019t evidence for an interstellar origin, because meteorites only sample a fraction of materials in our solar system.\u201d<\/p>\n \u201cThese are things that have been sitting on the seafloor [for] at least nine years, but frankly probably thousands of years, reacting with seawater and collecting contamination,\u201d says Steven Desch at Arizona State University. \u201cThe ocean floor is littered with all sorts of things \u2013 there are natural explanations.\u201d<\/p>\n The nature of IM1 itself has come under fire, too. \u201cThere\u2019s every reason to think that these velocities, which don\u2019t have error bars, which cannot be checked, are not correct,\u201d says Desch. \u201cFor all of the fastest objects that seem to come from outside the solar system, there\u2019s almost always something wonky with the velocity \u2013 this object isn\u2019t established as interstellar at all.\u201d Plus, it\u2019s not clear that any material would have survived the meteor\u2019s fiery journey through Earth\u2019s atmosphere, he says.<\/p>\n It will take much more evidence to convince other astronomers that the spherules are truly interstellar. But Loeb says it\u2019s possible that more evidence will be available soon. \u201cWe have only analysed one-tenth of the materials, but I decided to put it out now so that we could get some feedback from the community. So if there\u2019s something we need to do differently or if we need to share some materials we can do that,\u201d he says. He and his colleagues are already planning another expedition to look for larger pieces of IM1.<\/p>\n