Not everyone is convinced by the idea, of course. Indeed most researchers think it is highly dubious. One scientist who posted a message on Louis's website described it as 'bullshit'.

But a few researchers believe Louis may be on to something and are following up his work. Milton Wainwright, a microbiologist at Sheffield, is now testing samples of Kerala's red rain. 'It is too early to say what's in the phial,' he said. 'But it is certainly not dust. Nor is there any DNA there, but then alien bacteria would not necessarily contain DNA.'

Critical to Louis's theory is the length of time the red rain fell on Kerala. Two months is too long for it to have been wind-borne dust, he says. In addition, one analysis showed the particles were 50 per cent carbon, 45 per cent oxygen with traces of sodium and iron: consistent with biological material. Louis also discovered that, hours before the first red rain fell, there was a loud sonic boom that shook houses in Kerala. Only an incoming meteorite could have triggered such a blast, he claims. This had broken from a passing comet and shot towards the coast, shedding microbes as it travelled. These then mixed with clouds and fell with the rain. Many scientists accept that comets may be rich in organic chemicals and a few, such as the late Fred Hoyle, the UK theorist, argued that life on Earth evolved from microbes that had been brought here on comets. But most researchers say that Louis is making too great a leap in connecting his rain with microbes from a comet.

For his part, Louis is unrepentant. 'If anybody hears a theory like this, that it is from a comet, they dismiss it as an unbelievable kind of conclusion. Unless people understand our arguments - people will just rule it out as an impossible thing, that extra-terrestrial biology is responsible for this red rain.'

Experts at the local meteorology centre said sand from neighboring Mongolia was to blame for this unusual natural phenomenon.
Before it arrived in Maritime, the cyclone passed Mongolia, where sand storms had been raging in the desert.

"The winds of the cyclone embraced dust particles that colored the fallouts," the experts said.

February's yellow snowfall with a strong odor and an oily texture was observed on Russia's Far East island of Sakhalin. The color, odor and texture of the snow may have been a result of environmental pollution caused by the island's oil and natural gas industry.

However, experts do not rule out this could be caused by volcanic activity.

Recent high-resolution images snapped by the orbiting Cassini confirmed the eruption of icy jets and giant water vapor plumes from geysers resembling frozen Old Faithfuls at Enceladus' south pole.

"We have the smoking gun" that proves the existence of water, said Carolyn Porco, a Cassini imaging scientist from the Space Science Institute in Boulder, Colo.

"The simple fact that this exists apparently in liquid form near the surface really puts Enceladus in a class by itself," Harwood said. "Aside from earth, there is nowhere in the solar system where there is liquid water so near a surface. Even Mars doesn't have reservoirs like this, as far as we know."

If Enceladus does harbor life, it probably consists of microbes or other primitive organisms capable of living in extreme conditions, scientists say.

David Morrison, a senior scientist at NASA's Astrobiology Institute, cautioned against rushing to judgment about whether the tiny moon could support life. Scientists generally agree habitats need several ingredients for life to emerge, including water, a stable heat source and the right chemical recipe.

"It's certainly interesting, but I don't see how much more you can say beyond that," Morrison said.

Scientists believe Mars and Jupiter's icy moons might have - or once had - conditions hospitable to life.

Enceladus measures 314 miles across and is the shiniest object in the solar system.

It was long thought to be cold and still. But scientists now believe it is a geologically active moon that possesses an unusually warm south pole.

The water is believed to vent from fissures in the south pole. Porco said the venting has probably been going on for at least several thousand years, potentially providing a lasting heat source.

The Cassini-Huygens mission is a joint NASA-European Space Agency project. The spacecraft was launched in 1997 and went into orbit around Saturn in 2004, exploring its spectacular rings and many moons. Cassini made three flybys of Enceladus last year and is expected to fly within 220 miles of the moon again in 2008.