Europa, Jupiter's fourth-largest moon, has been hailed as one of the most likely locations for aliens to exist in our solar system. 

Now NASA may have the chance to find out, as its ambitious Europa Clipper mission is set to launch on a five-and-a-half-year journey to investigate. 

After a delay caused by Hurricane Milton, Clipper will launch from NASA's Kennedy Space Center in Florida at 12:06 ET (17:06 BST) today.

Following an approximately 1.8billion-mile trip, the $5.2 billion (£4billion) spacecraft is expected to start orbiting Jupiter in April 2030.

During more than 40 flybys, Clipper will conduct a detailed survey of Europa to determine whether the icy world 'could have conditions suitable for life'.  

Slightly smaller than Earth's moon, Europa is considered one of the solar system's most promising potentially habitable environments. 

Along with Earth and Saturn's moon Enceladus, Europa is one of the very few locations in our solar system with liquid water. 

Live coverage of today's launch will stream on NASA+ and NASA's YouTube channel.   

'There is very strong evidence that the ingredients for life exist on Europa, but we have to go there to find out,' said Dr Bonnie Buratti, from NASA's Jet Propulsion Laboratory and the mission's deputy project scientist.

Dr Buratti said exploratory missions such as this one always uncover something 'that we could not have imagined'. 

'There is going to be something there - the unknown - that is going to be so wonderful that we can't conceive of it right now,' she said. 'That's the thing that excites me most.'  

One of Jupiter's 95 known moons, Europa is encased in an ice sheet estimated to be 10 to 15 miles (15 to 24km) or more thick. 

Scientists believe this frozen crust hides a saltwater liquid ocean that could be 80 miles (120 km) or more deep and hold about twice as much water as Earth's oceans combined – and possibly harbor life. 

Clipper is the biggest spacecraft NASA has ever built for a planetary mission, measuring about 100ft (30.5 metres) with its solar arrays deployed – bigger than a basketball court. The solar arrays will gather sunlight for powering scientific instruments, electronics and its other systems.

Clipper's key mission objectives are producing high-resolution images of Europa's surface, determining its composition and looking for signs of recent or ongoing geological activity.

The mission will also measure the thickness of the moon’s icy shell, search for subsurface lakes and determine the depth and salinity of Europa's ocean.

In this animation, Clipper (pink) departs Earth (blue). It swings past Mars (brown) early next year and then Earth again in late 2026 as it builds up speed. Finally, after an approximately 1.8billion-mile journey, Europa Clipper enters orbit around Jupiter (green) in April 2030

Dr Buratti notes that there are three main requirements for life to form in our solar system – liquid water, certain chemistry (organic compounds that could serve as food for any primitive organisms) and an energy source. 

In Europa's case, an energy source could be thermal vents on the ocean floor. Experts think there could be microbes deep down in this potentially nutrient-rich liquid ocean, which could be a lot warmer than the outer shell thanks to the thermal vents. 

Alternatively, the lifeforms may be adapted to survive in extremely frigid temperatures. These lifeforms could be tiny, such as 'extremophile' microbes that would be invisible to the naked human eye. 

A hugely promising finding by the James Webb space telescope last year was the presence of carbon dioxide (CO2) on Europa.

The 'biologically essential' compound could be produced by lifeforms much like humans produce CO2 on Earth. 

Last year, scientists found there's less oxygen on Europa's surface than previously thought, which is crucial for cells to be able to function. Although it didn't completely rule out the possibility of life on Europa, the study said there's a 'narrower range to support habitability' than we realised. 

Dr Buratti thinks any life on Europa would be primitive like the bacterial life that originated in Earth's deep ocean vents. 

However, she stresses that Clipper will not look directly for signs of life but will instead determine if the moon contains the 'ingredients' that would allow life to be present.

If it does, another mission would then have to make the journey to try to detect it – for example, by drilling down through the icy shell. 

'We will not know from this mission because we can't see that deep,' Dr Buratti said. 

When it completes its journey more than five years from now, Clipper will not enter orbit around Europa, but will instead orbit Jupiter. 

As it's orbiting Jupiter, it will conduct 44 flybys of Europa, each at altitudes ranging from 16 miles to 1,678 miles (25km to 2,700km) during its 3.5-year mission. 

In September 2022, another NASA probe called Juno past within 220 miles (355 km) of the moon's frozen surface.

But Clipper will sneak within 16 miles (25km) Europa's surface – closer than any other spacecraft. 

When its work is done in 2034, the mission will end with a planned crash into Ganymede – Jupiter and the solar system's biggest moon.