Saturn moon’s mysterious vapour plumes could be key to alien life

March 17th, 2008 - 2:54 pm ICT by admin  


DPA
Hamburg (Germany), March 17 (DPA) Scientists on NASA’s Cassini mission are counting on the probe’s next fly-by to provide them with possible clues to alien life following discovery of water vapour plumes on a moon of Saturn. The spacecraft will zoom in on the moon Enceladus in March. Its closest approach will be at a mere 50 km from the surface and the altitude will increase to about 200 kilometres as the spacecraft passes through the plumes.

Cassini will sample the plumes directly and find out more about their composition, said German scientists who are monitoring the data.

Enceladus is jetting out giant geysers three times the size of the moon, and now the German scientists are beginning to understand how the ice grains are created and how they might have formed.

Knowing the process of how the plume forms and the path the water-ice particles have to travel is giving them an insight into what may be a liquid reservoir or lake lying just beneath the surface - which might possibly be simple alien lifeforms of some sort.

“Since Cassini discovered the water vapour geysers, we’ve all wondered where this water vapour and ice are coming from. Is it from an underground water reservoir or are there some other processes at work?

“Now, after looking at data from multiple instruments, we can say there probably is water beneath the surface of Enceladus,” said Juergen Schmidt, team member on Cassini’s Cosmic Dust Analyzer at the University of Potsdam, Germany.

This study appeared in the journal Nature.

The large number of ice particles observed spewing from the geysers and the steady rate at which these particles are produced require high temperatures, close to the melting point of ice, possibly resulting in an internal lake.

The lake would be similar to Earth’s Lake Vostok, beneath Antarctica, where liquid water exists locked in ice. The ice grains then condense in the vapour evaporating from the water, streaming through cracks in the ice crust to the surface.

The presence of liquid water inside Enceladus would have major implications for future astro-biology studies on the possibility of life on bodies in the outer solar system.

Scientists have studied the plume dynamics since 2005, collecting data from several Cassini remote sensing instruments and those that sample particles directly, like the Cosmic Dust Analyser.

They conclude that an internal lake at a temperature of about 273 Kelvin (zero degrees Celsius or 32 degrees Fahrenheit) is the best way to account for the material jetting out of the geysers.

While that sounds cold to us on Earth, in the depths of the outer solar system, that is a balmy temperature.

At these “warm” temperatures, liquid water, ice and water vapour mingle. The vapour escapes to the vacuum of space through cracks in Enceladus’ ice crust.

When the gas expands, it cools and the ice grains that make up the visible part of the plumes condense from the vapour. Vapour in the plumes is clocked at roughly the same speed as a supersonic jet, about 300 to 500 metres per second, or about 1,000 km (650 miles) per hour.

Most of the particles, which have lost energy through collisions in transit, fail to achieve escape velocity and fall back to Enceladus’ surface. Only about 10 percent escape Enceladus and form Saturn’s E-ring.

“Our model provides a simple concept to understand how particles form, their speed and how they behave as they make their way out into space. If vapour temperature is too low, then the gas density is too small to push the grains out and we would not see such large amounts of particles,” said Schmidt.

“Therefore, we believe that at the site of evaporation, we must have temperatures near the melting point of water.”

This research provides fundamental knowledge of solar system bodies, in particular those that, like our home planet, are homes to oceans - environments where life might evolve.
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