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As soon as Rosetta entered orbit around comet 67P/Churyumov-Gerasimenko in August, engineers rushed to find a landing site for its Philae lander - which they have now done.

Why? Because as the comet nears the sun it will become more active, with more potentially hazardous vapour and debris released.

And that activity has been revealed in images showing how the comet is indeed giving off jets of water - but scientists aren't quite sure why.

Jets of water vapour have been spotted in images of Rosetta's comet target. The material is being shot into space, but it's unclear why it appears as 'jets'. Emily Lakdawalla of The Planetary Society spotted the jets by brighting photos from Rosetta (move the slider above to see the 'before' and 'after' effect)

The jets of water vapour were revealed by Emily Lakdawalla of The Planetary Society.

By increasing the contrast on available shots of the comet, she revealed previously hidden jets of water vapour spewing outwards.

And scientists will be hoping to study these jets in more detail as the comet approaches the sun, and possibly work out exactly how they form and what they're made of.

'The challenge with Rosetta's images of the comet is that until quite recently, most of them were taken with the sun nearly behind the spacecraft,' Ms Lakdawalla told MailOnline.

'That lights up the comet's surface very brightly compared to the much fainter comet jets.

'But the jets are there; all you have to do is brighten the image to reveal them, an operation anyone can do with the most basic photo editing software.

'The work I did was to combine a brightened image of the jets with an unbrightened image of the comet, so it's an artistic enhancement of the original image.

'It's much like a film photographer would dodge a photo to brighten some areas compared to others.

'I also cleaned up some distracting specks and cosmic ray hits, which make white marks on the original photos.'

As Rosetta spends more time on the night side of the comet Lakdawalla says it will be easier to spot jets coming off the comet as the surface will not be so bright.

She continues: 'Every day brings the comet closer to the sun and makes it more active. 

'That will be exciting to watch, but it presents a challenge for Rosetta. 

'The jets and the gas around the comet will influence Rosetta's path in unpredictable ways, making it hard for them to steer precisely, which will make it hard for them to place Philae where they want to put it on the surface. 

'That is one reason they're in such a hurry to select a landing site and land Philae - it will get harder to achieve as the comet gets more active.'

As the comet (seen in this 'selfie' with Rosetta) approaches the sun it will become more active. Ice remaining on the surface will melt, surrounding the comet in gas. For this reason engineers want to perform the planned landing of the Philae lander on the comet as soon as possible before too much vapour is present

In November the Rosetta probe will launch its Philae robot from a distance of about 6.2 miles (10km) to 67P. If all goes to plan, Philae will then make a gentle landing on the comet at walking pace. The lander will drill and collect samples from beneath the surface, delivering them to an onboard laboratory for analysis

Earlier this week scientists picked landing site 'J', shown, as the location where the Philae lander will touch down. ite J offers the minimum risk to the lander in comparison to the other candidate sites, and is also scientifically interesting, with signs of activity nearby

 In addition, while the jets are mostly made of water vapour, Rosetta's Miro (Microwave Instrument for the Rosetta Orbiter) instrument has also spotted expected signs of ammonia and methanol in the jets - although a lack of carbon monoxide has been a surprise.

They are also thought to carry ice crystals and dust specks with them from the surface.

One thing that is not known however is why the jets are actually appearing as 'jets'.

As a comet nears the sun its surface sublimates, which means the solid ice turns to gas, creating a 'coma' of material around the comet.

Why Rosetta's comet is only spewing material at specific points in jets, rather than across the whole surface, remains a mystery.

'That is one of the as yet unanswered questions about comets that Rosetta's scientific data will hopefully address,' added Ms Lakdawalla.

'One thing to remember is that short-period comets like 67P/Churyumov-Gerasimenko have been baked by the sun for a long time so their surfaces are not covered with ice but rather with very dark dust.

'It looks bright in Rosetta pictures only because we're looking at a dark object against even darker space, and the camera's exposure settings have been adjusted accordingly - try taking a digital photo of a charcoal briquet against an asphalt-covered street and see how bright the auto-exposure on your camera makes the charcoal appear!

'The ice we see coming out of it is being released from the interior, through fissures or craters. But how this process works isn't understood, yet.

'By orbiting a comet for many months and watching it become more active, Rosetta is the first mission that has a chance of answering these questions.' 

Zoom in on the image below to find out where Rosetta is at the moment