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On 26 May, JPL's unique orbital calculation software determined that Comet Catalina was on what could possibly be a collision course with Earth, though the odds of such an impact were small: just 1 chance in 300,000 of a strike on June 11, 2085. Based on the 980-metre size estimate, that would produce a 6-gigaton impact - equivalent to 6 billion tonnes of TNT. Astronomers expected the addition of further observations to the calculations to rule out any possibility of a collision, as happens with most newly-seen objects. But that did not quite happen. The comet's predicted pathway actually drew...

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Abstract: The young Earth appear to have been bombarded by comets for several hundred million years shortly after it was formed. This onslaught, perhaps involving hundreds of millions of comet impacts, is currently the best explantion for the origin of the Earth’s oceans, atmosphere and organic molecules. Although historically a controversial idea, there is now a considerable amount of physical and chemical evidence supporting the theory. Comet scientist Armand Delsemme reviews the evidence and argues that comets from the vicinity of Jupiter contributed the bulk of the constituents found in Earth’s biosphere.

Did comets flood Earth’s oceans? Did comets flood Earth's oceans? 16 June 2004 Did the Earth form with water locked into its rocks, which then gradually leaked out over millions of years? Or did the occasional impacting comet provide the Earth’s oceans? The Ptolemy experiment on Rosetta may just find out… The Earth needed a supply of water for its oceans, and the comets are large celestial icebergs - frozen reservoirs of water orbiting the Sun. Did the impact of a number of comets, thousands of millions of years ago, provide the Earth with its supply of water? Finding hard...

The Mars rover Opportunity's examination of Martian rocks last week provided the first convincing evidence that our neighbour world was once "awash" in water, as one NASA scientist described it. But where did the water come from? And why does Mars have no liquid water now, while Earth apparently has been covered with the stuff for 4 billion years? Scientists are just beginning to piece the story together, and it goes right back to the beginning. Mars, like Earth, was formed from dusty and rocky debris left over after the sun was born 4.57 billion years ago. Initially, there were...

The pre-dawn phenomenon, which looks like a huge bubble expanding and then popping, was recorded June 22 by the Canada-France-Hawaii Telescope and the Subaru Telescope. Since then, speculation has run rampant about the source of the early morning flash. Ichi Tanaka, a support astronomer at Subaru Telescope, describes it as "a huge halo of light above the eastern horizon," adding, "It was slowly expanding to over 45 degrees in five minutes or more."