text: After four years orbiting the closest planet to our sun, the Messenger spacecraft will this week make a death-dive into Mercury. But the probe hasn't finished its mission  yet, with new, detailed views emerging of the planet as Messenger spirals closer to its surface. Now Nasa has released an image taken by the probe's Visual and Infrared Spectrometer (Virs) revealing distinct features such as volcanic vents and fresh craters. Nasa has released an image taken by the probe's Visual and Infrared Spectrometer (Virs) to reveal distinct features such as volcanic vents and fresh craters. To highlight the geological features, the images have been overlain on a black and white mosaic from the Mercury Dual Imaging System (MDIS) To highlight the geological features, the images have been overlain on a black and white mosaic from the Mercury Dual Imaging System (MDIS). This is an instrument with wide- and narrow-angle cameras that has been mapping the rugged landforms on Mercury’s surface. The spacecraft is expected to smash into the planet's surface at 2.4 miles per second (3.9km/s). The event will take place on Thursday 30 April at 3:30pm Eastern Time (7.30pm GMT). However, when it does, Messenger will be behind Mercury, and hidden from Earth. 'The last couple of hours will probably be pretty quiet,' Mercury mission head Sean Solomon told Nature. 'There will be a final orbit when the spacecraft passes behind the planet and we won't hear from it again. 'I have worked on the mission for 19 years. It's like losing a member of the family. Even pre-knowledge doesn't prepare you completely for the loss.' The Mercury Dual Imaging System (MDIS) is an instrument with wide- and narrow-angle cameras that has been mapping the rugged landforms on Mercury’s surface. It was used to helped create these images of Mercury . The spacecraft is expected to smash into the planet's surface on Thursday 30 April after a four-year mission . Among the features Messenger has revealed to scientists in the past month are patterns of distinctive hollows - each around a couple of hundred metres wide - in the bottom of a huge impact basin. It has also sent back detailed images of huge 1.2 mile (2km) high cliffs that cut across a crater named Duccio on the surface. Another image shows a 621 miles (1,000km) long cliff that rises 1.8 miles (3km) above the surface, called Enterprise Rupes. Researchers have uncovered the mystery of Mercury's 'stealth' colour scheme. The say a steady dusting of carbon from passing comets has slowly painted Mercury black over billions of years. It solves the mystery of Mercury's unusual colouring - which has baffled scientists. On average, Mercury is much darker than its closest airless neighbour, our Moon. Airless bodies are known to be darkened by micrometeorite impacts and bombardment of solar wind, processes that create a thin coating of dark iron nanoparticles on the surface. But spectral data from Mercury suggests its surface contains very little nanophase iron, certainly not enough to account for its dim appearance. As comets approach Mercury's neighborhood near the sun, they often start to break apart. Cometary dust is composed of as much as 25 percent carbon by weight, so Mercury would be exposed to a steady bombardment of carbon from these crumbling comets. Scientists have calculated that after billions of years of bombardment, Mercury's surface should be anywhere from three to six percent carbon. Data sent back by Mercury suggests these cliffs, or lobate scarps as they are called, have formed as Mercury has cooled and contracted over time, creating dramatic tectonic faults on the surface. Another image shows a meteorite crater that has almost completely filled with lava on Mercury's northern volcanic plains, leaving just the hint of a rim behind. It also shows how the contracting surface of the planet has also created strange formations where ridges and cliffs have hit other lava filled craters. Among the images sent back by Messenger as its mission draws to an end is this picture of 1.2 mile-high (2km) cliffs cutting through the Carnegie crater. They are thought to have formed as Mercury cooled . Distinctive hollows on the floor of the Zeami impact basin on Mercury can be seen in this Messenger image . Andy Calloway, Messenger Mission operatoins manager at Johns Hopkins Applied Physics Laboratory, said: 'The Messenger spacecraft operates in one of the most challenging and demanding space environments in our solar system. 'We have met that challenge directly through innovation and hard work, as exemplified by the stunning discoveries and data return achievements. 'Our only regret is that we have insufficient propellant to operate another 10 years, but we look forward to the incredible science returns planned for the final eight months of the mission.' Launched in August 2004, Messenger has traveled more than 4.9 billion miles (7.9 billion kilometers) during its mission to Mercury. Its journey included 15 trips around the sun before it entered orbit around Mercury in 2011 - the first spacecraft to ever do so. During its mission is has acquired more than 250,000 images and collected more than 10 terabytes of data with its suite of seven instruments. It has helped reveal volcanic vents that measure up to 15 miles (24km) across that were once sources for the large volumes of lava that have covered the surface and carved out valleys. It has also revealed Mercury's complex internal structure and that the planet has an unusually large core that is still partially liquid. On 6 April engineers used the last of the Messenger spacecraft's hydrazine fuel to try to push it into a higher orbit. However, the tanks ran dry before they could raise it to more than 11 miles (18km) above the surface. This image shows some of the mysterious irregularly shaped hollows on Mercury's surface in greater detail . The above artist's impression shows Messenger as it orbits above the surface of Mercury. It is due to impact on the surface at the end of April as the planet's gravity slowly pulls it down out of its current orbit . Messenger has also revealed the temperature of Mercury's surface. This image of the planet's north pole shows the extreme heat it is subjected to with red indicating temperatures greater than 126°c and blue -220°c .
target: Messenger is expected to hit the surface of Mercury on April 30 .
  Probe has been orbiting Mercury since 2011, taking 250,000 pictures .
  Latest image shows features such as volcanic vents and fresh craters .