The comet Ison may have survived its journey close to the sun, scientists say.

Many researchers predicted the comet would be destroyed by the star's heat and gravitational forces as it passed through its perihelion - the point at which passed closest to the sun.

Experts at the European Space Agency, who previously declared the comet had been destroyed, have conceded that a small fragment of the comet may still be intact.

Scientists have been debating and analysing images taken by Nasa's Solar and Heliospheric Observatory (Soho) since the comet passed its perihelion.

Initially astrophysicists feared the ball of ice and dust had died after Soho images suggested it had dulled. But the latest telescopic images, which show a brightening of what may be the comet's nucleus, have reignited hopes that part of the comet remains. The fragment may become brighter or simply fade away; experts will continue to study the comet's images and trajectory to try to predict its course over the coming days and weeks.

Karl Battams from the US space agency-funded Sungrazing Comets Project told the BBC that comet Ison continued to surprise and confuse scientists.

"It's just typical that right at the end, when we said, 'yes, it has faded out, it's died, we've lost it in the Sun', that a couple of hours later it should pop right back up again," he said.

Another comet, Siding Spring, is predicted to pass by Mars in October 2014, but whether it will appear in the inner solar system is not known.