As you will no doubt have noticed, the Curiosity rover has successfully landed on Mars. Its mission is to explore the planet’s surface, with a particular emphasis on searching for any signs that life once existed on Mars. There may be traces of bacteria or other simple organisms and if there are then the rover has tools it can use to identify them.
The project has taken ten years to reach this point and there was very obvious relief in the control room when the first signals from Curiosity made it back to Earth. The landing process was very complicated, as the video below brilliantly describes.
The BBC writes “The descent through the atmosphere after a 570-million-km journey from Earth had been billed as the “seven minutes of terror” – the time it would take to complete a series of high-risk, automated manoeuvres that would slow the rover from an entry speed of 20,000km/h to allow its wheels to set down softly.”
I am a little confused by a 570 million km journey. Theoretically, when Earth is at its furthest distance from the Sun (aphelion) and Mars is at its closest (perihelion), Mars and Earth are about 54 million km apart. They can be as far apart as 401 million km when they are on opposite sides of the Sun. Presumably, NASA would have opted for a launch time that coincided with Mars and Earth being fairly close – at least, that’s what I would do! The Sun is 150 million km away from Earth (on average) so 570 million km is a substantial journey. The NASA press pack says that the distance between Earth and Mars on the day of launch was 204 million km and that by the landing date the two planets were 248 million km apart. They then confirm that the journey distance has been 567 million km. I am being dim and can’t quite get my head around it!
The radio signals, which travel at the speed of light, take slightly under 14 minutes to reach Earth from Mars. You could describe Mars as being 13.8 light minutes away. If you were thinking of going to Mars on holiday, you should pack an extra pair of thick socks as the surface temperature ranges from a high of 0 degrees Celsius to a night time low of -90 degrees Celsius. Mars takes 98 Earth weeks to orbit the Sun once (a Martian year) and that is the hoped for length of the rover’s mission. It will travel up to 200 metres per day, powered by a nuclear electrical generator and lithium-ion batteries. The NASA .pdf file is a good read if you are interested in all the facts and figures surrounding the mission – http://www.jpl.nasa.gov/news/press_kits/MSLLanding.pdf.
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