After a nine year wait, NASA's New Horizons space probe has become the first probe to successfully reach Pluto, although scientists had to endure some agonising hours waiting to receive its ‘phone home’ signal as it flew past the planet at over 30,000 miles per hour.

Due to the huge distances involved – the small, icy planet sits at the periphery of the solar system some 4.67 billion miles from Earth – the transmission time for radio signals from mission control is over four hours. In fact, in the time taken for the New Horizons probe to travel through space since its launch in 2006, scientists have even reclassified Pluto, from a planet to a dwarf planet, reflecting its minimal 1,413 mile diameter.

After its extraordinarily long and arduous journey, New Horizons passed Pluto at a distance of only 7,800 miles, travelling on autopilot as it photographed the planet and its moons and taking measurements that will provide scientists with more data on what Pluto is made of and which gases comprise its atmosphere. However, due to the initial delay in receiving information from the probe, NASA’s mission controllers faced an anxious wait to discover if New Horizons survived its flyby.

One of the most dangerous threats to the probe was the possible presence of dust particles from Pluto or its moons. Even a tiny grain of dust could, at the colossal speed at which New Horizons is travelling, have caused irreparable damage to the probe, bringing the entire project to an immediate end.

However, while the mission was untested and the first of its kind, scientists were confident of avoiding catastrophe on this occasion, with the chances of disaster estimated to be less than 0.0001%. Nevertheless, the delay in receiving the first signals from the probe to confirm its safe passage past Pluto meant an air of uncertainty lingered over mission control.

Pluto remains one of the most elusive and secret bodies in the solar system. Less than two thirds the size of the Moon, it is made mainly of rock and ice, although its exact surface constituents and gaseous atmosphere remain something of a mystery. Since its discovery in 1930, Pluto has only completed two-thirds of its 248 year orbit of the sun. The $700 million New Horizons project will provide scientists with more information about these aspects of Pluto as well as measuring the temperature and air pressure in the atmosphere to determine how much gas is escaping into space. Already, on its approach to its destination, the probe has sent back some tantalising photographs of Pluto and its moons, and the first pictures taken from close by have wowed the scientific community world over.

However, most of the data New Horizons collects will not be sent back to mission control in Maryland until September; consequently, it could take many months to accumulate all the information about the solar system’s most mysterious body.