Nasa reveals comet that grazed Mars Comet passed just 87,000 miles (140,000km) from the red planet Tonnes of comet dust bombarded the Martian sky Created incredible scene of thousands of fireballs an hour. Warped the Martian atmosphere leaving metals and a yellow afterglow Opportunity rover on the surface returned an image of the comet Event provided unprecedented opportunity for researchers to gather data Siding Spring comes from the Oort Cloud in the outer solar system By Mark Prigg and Jonathan O'Callaghan for MailOnline It was one of the most incredible displays ever seen - yet only a handful of rovers and spacecraft were there to witness it. Nasa has revealed the data its spacecraft gathered when Comet Siding Spring, which passed just 87,000 miles (139,500 km) by Mars on Oct. 19. Experts describe the scene, with thousands of shooting stars per hour and the entire sky changing colour as 'mind blowing'. Comet Siding Spring approaching Mars, shown with Nasa's orbiters preparing to make science observations of this unique encounter. A pristine distant comet created a once-in-eight-million-year fireworks show on Mars and no humans were there to witness it. Nasa's five robotic explorers at Mars - three orbiters and two rovers - were repurposed to witness the comet named Siding Spring make its first known visit to the inner solar system. So too were a European and an Indian spacecraft circling the red planet. The orbiting craft attempted to observe the incoming iceball, then hid behind Mars for protection from potentially dangerous dusty debris in the comet tail. And on the surface of Mars the active rovers Opportunity and Curiosity were also used to observe the comet in the sky. At twilight, the Martian skies likely took on a yellowish hue from sodium in vaporized comet dust, creating a glow similar to sodium vapor lights commonly used in parking lots on Earth. 'To see (that) many shooting stars happening at once, I think it would have been really mind-blowing,' planetary scientist Nick Schneider, with the University of Colorado in Boulder, told reporters on a conference call. Scientists used a fleet of robotic spacecraft circling Mars to study Comet Siding Spring, which passed just 87,000 miles (139,500 km) by Mars on Oct. 19. That was less than half the distance between Earth and the moon, and 10 times closer than any known comet that has passed by Earth. The comet was a rare visitor from the Oort Cloud, a spherically shaped reservoir beyond Neptune's orbit containing leftovers from the formation of the solar system some 4.6 billion years ago. Comet Siding Spring 'probably has never been in to the inner solar system before,' said Jim Green, head of NASA's Planetary Science Division in Washington. The comet also left an imprint on Mars, depositing thousands of pounds of dust into the atmosphere, far more than computer models had predicted. NASA had moved its orbiting spacecraft so they would be behind Mars and shielded from dust impacts at the peak of the storm. 'I really believe that hiding them like that really saved them,' Green said. We ended up with a lot more dust than we ever anticipated. This handout artist's concept provided by NASA/JPL shows the Comet Siding Spring approaching Mars. When Comet Siding Spring skimmed the red planet, tons of comet dust bombarded the Martian sky with thousands of fireballs an hour. It warped the Martian atmosphere leaving all sorts of metals and an eerie yellow afterglow. Measurements taken before and after Siding Spring's approach show significant changes in Mars' upper atmosphere, including the addition of a new layer of charged particles and telltale chemical fingerprints of magnesium, iron and other metals shed by the passing comet. Analysis is ongoing to determine the comet's size, composition and other attributes. The comet is named for the Australian observatory that discovered it last year. More images of the remarkable once-in-a-million-year event, that saw a comet hurtle past Mars, have emerged. After Opportunity snapped an image from the surface, an image from one of the Martian orbiters has been released. And astronomers on Earth also managed to capture the extremely rare cosmic event. These images were taken of comet C/2013 A1 Siding Spring by Nasa's Mars Reconnaissance Orbiter on 19 October 2014 during the comet's close flyby of Mars and the spacecraft. It is the highest-resolution image of a comet that heralds from the Oort Cloud at the edge of the solar system ever taken The High Resolution Imaging Science Experiment (HiRISE) camera on Nasa's Mars Reconnaissance Orbiter (MRO) was used to capture views of comet C/2013 A1 Siding Spring. The amazing images are the highest-resolution views ever acquired of a comet coming from the Oort Cloud at the fringes of the solar system. And the images have been used to estimate that the nucleus of the comet is roughly half the size originally thought, making it about a quarter of a mile (0.4km) wide. The HiRise camera on the MRO acquired images of this comet from a minimum distance of about 86,000 miles (138,000 kilometers), yielding a scale of about 453 feet (138 meters) per pixel. Another image taken by Nick Howes using the Tzec Muan Observatory in Australia reveals the comet and its tail as it approaches Mars. The amazing picture sees Mars look almost as bright as the sun as the image had to be overexposed in order to reveal the comet. This image of Comet Siding Spring was taken by astronomers Nick Howes and Ron Wodaski using the Tzec Muan Observatory in Australia. The comet is the blue-ish object towards the middle of the picture, with its tail seen streaking backwards. Mars is the bright sun-like object in the middle, overexposed to reveal the comet 'We'd planned our observations for weeks in advance, scripting telescope code and setting up observation plans,' Mr Howes told MailOnline. 'We shot hundreds of images of the comet and Mars with different exposure times, and had some technical challenges to overcome, but we're delighted with the end result, which was part of a global collaboration with both professional and amateur observers. Tzec Muan is an educational outreach observatory, so this is great motivation also for the students Comet C/2013 A1, also known as Siding Spring, passed within about 87,000 miles (140,000 km) of Mars, equivalent to about one-third of the distance between Earth and our moon. Nasa confirmed yesterday that all three of its Mars orbiters survived the event unscathed, while Esa and India's spacecraft were also unaffected. The event will provide an unprecedented opportunity to gather data on both the comet and its effect on the Martian atmosphere. This incredible image showing the comet in the Martian sky was taken by Nasa's opportunity rover on the surface of Mars - the first ever image of a comet from another planet. It is hoped the event will provide researchers with an unprecedented opportunity to gather data on comets Three Nasa Mars orbiters, two Mars rovers and other technologies on Earth and in space were used to study comet Siding Spring. 'All 3 Mars orbiters confirmed healthy after taking shelter behind Mars,' Nasa confirmed in a tweet. To keep the orbiting spacecraft safe they had been positioned on the other side of the planet, away from the comet and its potentially damaging tail of dust. However, as the comet approached Mars the spacecraft were used to take images and record data. The comet is making its first visit this close to the sun from the outer solar system's Oort Cloud, so the concerted campaign of observations may yield fresh clues to our solar system's earliest days more than 4 billion years ago. 'Think about a comet that started its travel probably at the dawn of man and it's just coming in close now,' said Dr Carey Lisse, a senior astrophysicist at the Johns Hopkins University Applied Physics Laboratory, in a Nasa news briefing about Comet Siding Spring last week. And the reason we can actually observe it is because we have built satellites and rovers. We've now got outposts around Mars.' Siding Spring's nucleus came closest to Mars around 2:27pm EDT (7:27pm BST) on Sunday, hurtling at about 126,000 mph (203,000 km/h) relative to Mars. It's thought the comet is a remnant of the early solar system 4.5 billion years ago but has remained relatively unaltered since then. The comet passed its closest point just 87,000 miles (140,000 kilometres) from the red planet, and Nasa in Washington has confirmed all its spacecraft around Mars are safe. The agency took precautions to keep them all safe from the icy rock - illustrated approaching the red planet here It is also thought to complete a pass through the solar system every one or two million years, but it has never come this close to the sun. 'We cannot plan missions to comets like this - this one was discovered less than two years ago,' said Dr Mark Lemmon of Texas A&M University, a camera team member for NASA's Curiosity and Opportunity Mars rovers, in a statement. It is incredible luck that it is saving us the trouble of going to it, as it flies by Mars, which is being explored by seven active robots. So this very much is a once-in-a-lifetime event, for us and our rovers. Comet Siding Spring comes from the Oort Cloud, material left over from the formation of the solar system. This comet is coming into the solar system straight from the Oort Cloud. It's likely this is its first time this close to the sun,' said space scientist David Humm, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. Oort Cloud material, including comets, is scattered through a vast region that begins outside the orbits of Neptune and Pluto and extends a substantial fraction of the distance to Proxima Centauri, the closest neighboring star. Oort Cloud comets can tell scientists about the materials - including water and carbon compounds - that existed during the formation of the solar system some 4.6 billion years ago. The images above show - before and after filtering - comet C/2013 A1, also known as Siding Spring, as captured by Wide Field Camera 3 on NASA's Hubble Space Telescope. Studying this close encounter was the largest fleet of orbiting scientific observatories ever flown to another world, orbiting around (and rolling on the ground of) Mars. These instruments will, for the first time ever, have the chance to make close-up observations of a comet new to the inner solar system. And though it will not be the easiest task, the teams operating these instruments and spacecraft have developed plans to take advantage of this rare opportunity. Siding Spring is small (the nucleus is less than a mile in diameter) and fast (it passed Mars at about 34 miles/55 kilometres per second). The instruments on various spacecraft observed the comet repeatedly for two and a half days as it got closer and closer to Mars before it made its closest approach. The peak density of comet dust at Mars was expected 98 minutes after closest approach of the nucleus. This graphic shows the science observations that was hoped to be captured by Nasa's Mars spacecraft during the close encounter with Comet Siding Spring (C/2013 A1) The proximity of the comet will provide an unprecedented opportunity for researchers to gather data on both the comet and its effect on the Martian atmosphere. By studying Siding Spring's composition and structure, scientists hope to learn more about how the planets formed, according to Dr Lisse. Scientists also are keen to spot any changes to the comet or Mars due to the close approach. Nasa's newly arrived Maven spacecraft, for instance, will compare the upper atmosphere before and after it passes. 'Think about a comet that started its travel probably at the dawn of man and it's just coming in close now,' Dr Lisse said. 'We've now got outposts around Mars.' Scientists initially worried the spacecraft orbiting Mars would be at considerable risk from the comet's massive trail of dust. The nucleus itself poses no danger of impact. But the particles in the tail, hurtling through space at 126,000 mph (203,000 km/h), could fry electronics, puncture fuel lines, or destroy computers, transmitters or other vital spacecraft parts. As Siding Spring's path became clearer, the threat level was deemed minimal. Still, space agencies took no chances, employing the 'duck and cover' strategy. Nasa's three orbiters - Mars Odyssey, Mars Reconnaissance Orbiter and newcomer Maven - were behind the red planet at the time of peak danger - a 20-minute-or-so period approximately 1.5 hours after the closest approach by the comet's nucleus. Esa also shifted the orbit of its Mars Express as did India for its Mars Orbiter Mission, or MOM, the country's first interplanetary spacecraft that, like Nasa's Maven, arrived last month. The precautions are prudent, said University of Maryland senior research scientist Dr Tony Farnham, who led a hazard-analysis team. 'Comets are complex beasts and don't always live up to our predictions,' Dr Farnham said in an email Wednesday. 'If you don't want surprises, then don't study comets.' It will take at least a few days to obtain and analyze the best spacecraft data. Siding Spring should pass closest to the sun six days after its Mars flyby, then swing back out, bidding goodbye, for at least another million years. Nasa's Mars orbiters will gather information before, during and after the flyby about the size, rotation and activity of the comet's nucleus, the variability and gas composition of the coma around the nucleus, and the size and distribution of dust particles in the comet's tail. Observations of the Martian atmosphere are designed to check for possible meteor trails, changes in distribution of neutral and charged particles, and effects of the comet on air temperature and clouds. Maven will have a particularly good opportunity to study the comet, and how its tenuous atmosphere, or coma, interacts with Mars' upper atmosphere. Earth-based and space telescopes, including Nasa's iconic Hubble Space Telescope, also will be in position to observe the unique celestial object. The agency's astrophysics space observatories - Kepler, Swift, Spitzer, Chandra - and the ground-based Infrared Telescope Facility on Mauna Kea, Hawaii - also tracked the event.