Nasa has dismissed a controversial hypothesis by a Harvard astronomer suggesting that a rare interstellar object passing through the solar system could be a relic from an alien civilisation. The space agency says the object, known as Comet 3I/Atlas, behaves like a natural comet and poses no threat to Earth.
The theory was put forward by Avi Loeb, head of Harvard's Galileo Project, in a scientific paper published in July. Loeb noted that the comet has not shown the typical dusty, plasma tails seen on comets from within the solar system, and that its trajectory appears unusual. He suggested it could be a 'technological artifact' sent by design, possibly with malign intent, and warned that the consequences could be 'dire for humanity'.
However, Tom Statler, Nasa's lead scientist for solar system small bodies, rejected the claim. 'It looks like a comet. It does comet things,' he said. 'It very, very strongly resembles, in just about every way, the comets that we know.' He added that while the object has some unusual properties, the evidence overwhelmingly points to it being natural.
The comet, discovered on 1 July by the Atlas survey telescope in Chile, is only the third known object to enter the solar system from outside. Hubble Space Telescope imagery suggests it is up to 3.5 miles (5.6km) wide and travelling at 130,000mph (209,000km/h), the fastest speed ever recorded for a solar system visitor.
Statler confirmed that the comet will not come closer than about 170 million miles to Earth, though it will make close passes with Mars, Jupiter and Venus. He described the discovery as a rare opportunity to learn about other solar systems. Loeb, for his part, acknowledged that the simplest explanation is that 3I/Atlas is a comet, but maintained that exploring alternative ideas is a worthwhile exercise.
