CAPE TOWN -- Astronomers in South Africa will have a ringside seat for the biggest solar-system collision of the century when the first segments of a comet smash into Jupiter on Saturday.


Or it could turn out to be the biggest fizzle after months of excitement.


Astronomers from around the world have gathered at the Sutherland Observatory in the dry winter air of the semi-desert Karoo region, 275 kilometers northeast of Cape Town, to witness the comet Shoemaker-Levy 9 plunge into Jupiter.


The first of a string of comet fragments is due to hit the far side of the huge planet on Saturday at 23:54 Moscow time. The last is due on July 22.


Astronomer Dave Laney said the collision might be as cataclysmic as the one that scientists say could have ended the age of the dinosaurs on earth 65 million years ago.


But if the comet fragments disintegrate before they hit Jupiter, it will be no more than a meteor shower.


"All the little chunks will burn up in Jupiter's gaseous atmosphere and that will be it," said Laney, who is based at Cape Town's South African Astronomical Observatory.


"Some astronomers ... expect the sites of the impacts to be the size of continents, heated up to hundreds of degrees by the erupting fireballs. Others say the effect of the impacts will be little more than throwing a snowball at a mountain," said Hilda van Rooyen of the state science council, Foundation for Research Development.


One thing is certain, however. World attention will focus on the four telescopes under the 40-meter dome of the Sutherland Observatory as it transmits images of the first collision.


Observations will be impeded because the fragments will crash into the side of Jupiter facing away from Earth.


"But Jupiter rotates very rapidly, and within eight minutes of the impact the site of the crash will be visible," Laney said.


"We will be looking for reflections of the explosions on three of Jupiter's 16 moons. We'll also take electronic pictures in visible light and infra-red to look for plumes of gases from the impact and for new storms or other disturbances in the clouds.


"But even if we see nothing, that will actually tell us something. We will know much more about comets than we did before," Laney said.


Astronomers from New York, Hawaii, Japan and South Africa will operate the telescopes.


"Of all the world's observatories, only Sutherland is well placed to view the first impact on July 16," Laney said.


"It's all a matter of what hits Jupiter when, and where on Earth it is dark at that time," South African Astronomical Observatory director Bob Stobie said.