Telegraph | News

Earth punctured by tiny cosmic missilesTelegraph | News:

Earth punctured by tiny cosmic missiles
By Robert Matthews, Science Correspondent
(Filed: 12/05/2002)

FORGET dangers from giant meteors: Earth is facing another threat from outer space. Scientists have come to the conclusion that two mysterious explosions in the 1990s were caused by bizarre cosmic missiles.
The two objects were picked up by earthquake detectors as they tore through Earth at up to 900,000 mph. According to scientists, the most plausible explanation is that they were 'strangelets', clumps of matter that have so far defied detection but whose existence was posited 20 years ago.

Formed in the Big Bang and inside extremely dense stars, strangelets are thought to be made from quarks - the subatomic particles found inside protons and neutrons. Unlike ordinary matter, however, they also contain 'strange quarks', particles normally only seen in high-energy accelerators.

The scientists looked for events producing two sharp signals, one as it entered Earth, the other as it emerged again. They found two such events, both in 1993. The first was on the morning of October 22. Seismometers in Turkey and Bolivia recorded a violent event in Antarctica that packed the punch of several thousand tons of TNT. The disturbance then ripped through Earth on a route that ended with it exiting through the floor of the Indian Ocean off Sri Lanka just 26 seconds later - implying a speed of 900,000 mph.

The second event took place on November 24, when sensors in Australia and Bolivia picked up an explosion starting in the Pacific south of the Pitcairn Islands and travelling through Earth to appear in Antarctica 19 seconds later.

According to the scientists, both events are consistent with an impact with strangelets at cosmic speeds. In a report about to be submitted to the Seismological Society of America, the team of geologists and physicists concludes: "The only explanation for such events of which we are aware is passage through the earth of ton-sized strange-quark nuggets."

Professor Eugene Herrin, a member of the team, said that two strangelets just one-tenth the breadth of a hair would account for the observations. "These things are extremely dense and travel at 40 times the speed of sound straight through the Earth - they'd hardly slow down as they went through."