Telegraph | News: "Earth punctured by tiny cosmic missiles
By Robert Matthews, Science Correspondent
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.
Strangelets - sometimes also called strange-quark nuggets - are predicted to have many unusual properties, including a density about ten million million times greater than lead. Just a single pollen-size fragment is believed to weigh several tons.
They are thought to be extremely stable, travelling through the galaxy at speeds of about a million miles per hour. Until now, all attempts to detect them have failed. A team of American scientists believes, however, that it may have found the first hard evidence for the existence of strangelets, after scouring earthquake records for signs of their impact with Earth.
The team, from the Southern Methodist University in Texas, analysed more than a million earthquake reports, looking for the tell-tale signal of strangelets hitting Earth.
While their very high speed gives strangelets a huge amount of energy their tiny size suggests that any effects might be extremely localised, and there is unlikely to be a blast big enough to have widespread effects on the surface.
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."