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| Mars probe set for risky landing | Mars probe set for risky landing |
| (about 3 hours later) | |
| An American spacecraft is about to attempt a perilous landing on the surface of Mars. | An American spacecraft is about to attempt a perilous landing on the surface of Mars. |
| Nasa's Phoenix lander is due to touch down on Sunday GMT in the far north of the Red Planet, after a 680-million-km (423-million-mile) journey from Earth. | |
| The probe is equipped with a robotic arm to dig for water ice thought to be buried beneath the surface. | The probe is equipped with a robotic arm to dig for water ice thought to be buried beneath the surface. |
| Scientists say the mission should give the clearest indication yet of whether Mars could once have harboured life. | Scientists say the mission should give the clearest indication yet of whether Mars could once have harboured life. |
| The final seven minutes of the probe's ten-month journey is regarded as the riskiest part of the mission. | The final seven minutes of the probe's ten-month journey is regarded as the riskiest part of the mission. |
| The main goal of the mission is to get below the surface of Mars to where we are almost certain there is water Dr Tom Pike Phoenix Diary: Mission to Mars | The main goal of the mission is to get below the surface of Mars to where we are almost certain there is water Dr Tom Pike Phoenix Diary: Mission to Mars |
| After it enters the top of the Martian atmosphere at nearly 21,000km/h (13,000 mph), the probe must perform a series of manoeuvres to come safely to rest. | |
| It will release a parachute, use pulsed thrusters to slow to a fast walking speed, then come to a halt on three legs. | It will release a parachute, use pulsed thrusters to slow to a fast walking speed, then come to a halt on three legs. |
| If all goes to plan, the Phoenix lander will reach the surface of Mars at 0053 BST on 26 May (1953 EDT on 25 May). | |
| Nasa controllers will know in about 15 minutes whether the attempt has been successful. | Nasa controllers will know in about 15 minutes whether the attempt has been successful. |
| Phoenix will land further north than previous missions | Phoenix will land further north than previous missions |
| David Catling from the University of Bristol is a co-investigator on the mission. He said the landing phase would be one of the most exciting and tense parts of the journey, with so much riding on Phoenix's safe descent. | David Catling from the University of Bristol is a co-investigator on the mission. He said the landing phase would be one of the most exciting and tense parts of the journey, with so much riding on Phoenix's safe descent. |
| "Everyone involved is on tenterhooks and eager to start this unique exploration," he said. | "Everyone involved is on tenterhooks and eager to start this unique exploration," he said. |
| If all goes to plan, Phoenix will begin a three-month mission to search for ice beneath the Martian surface. | If all goes to plan, Phoenix will begin a three-month mission to search for ice beneath the Martian surface. |
| It will use a robotic arm to dig through the protective topsoil layer and lift samples of both soil and ice to its deck for scientific analysis. | It will use a robotic arm to dig through the protective topsoil layer and lift samples of both soil and ice to its deck for scientific analysis. |
| Building blocks | Building blocks |
| Dr Tom Pike of Imperial College, London, is part of the British team involved in the project. | Dr Tom Pike of Imperial College, London, is part of the British team involved in the project. |
| "The main goal of the mission is to get below the surface of Mars to where we are almost certain there is water," he told BBC News. | "The main goal of the mission is to get below the surface of Mars to where we are almost certain there is water," he told BBC News. |
| "The orbiters that are around Mars have already surveyed in great detail the area in which we are landing and we know that there is ice - solid water - 10cm, or maybe even less, below the surface. | "The orbiters that are around Mars have already surveyed in great detail the area in which we are landing and we know that there is ice - solid water - 10cm, or maybe even less, below the surface. |
| "Water, of course, is of critical importance because it is one of the building blocks - one of the essential habitats we need - for life." | "Water, of course, is of critical importance because it is one of the building blocks - one of the essential habitats we need - for life." |
| Landing on Mars is a notoriously tricky business. Of the 11 missions that have tried to land probes on Mars since 1971 - only five have succeeded. | Landing on Mars is a notoriously tricky business. Of the 11 missions that have tried to land probes on Mars since 1971 - only five have succeeded. |
| Phoenix carries seven science instruments | Phoenix carries seven science instruments |
| Phoenix is an apt name for the current mission, as it rose from the ashes of two previous failures. | Phoenix is an apt name for the current mission, as it rose from the ashes of two previous failures. |
| In September 1999, the Mars Climate Orbiter spacecraft crashed into the Red Planet following a navigation error caused when technicians mixed up "English" (imperial) and metric units. | In September 1999, the Mars Climate Orbiter spacecraft crashed into the Red Planet following a navigation error caused when technicians mixed up "English" (imperial) and metric units. |
| A few months later, another Nasa spacecraft, the Mars Polar Lander (MPL), was lost near the planet's South Pole. | A few months later, another Nasa spacecraft, the Mars Polar Lander (MPL), was lost near the planet's South Pole. |
| Phoenix uses hardware from an identical twin of MPL, the Mars Surveyor 2001 Lander, which was cancelled following the two consecutive failures. | Phoenix uses hardware from an identical twin of MPL, the Mars Surveyor 2001 Lander, which was cancelled following the two consecutive failures. |
| The probe was launched on 4 August 2007 on a Delta II rocket from Cape Canaveral Air Force Station in Florida. | The probe was launched on 4 August 2007 on a Delta II rocket from Cape Canaveral Air Force Station in Florida. |