'Curiosity' - NASA Mars Rover - Due to land 5th Aug 2012
Discussion
Yes 
Density obviously increases as altitude decreases. But also, density will vary at any given time due to the weather conditions encountered. Mars has changing areas of high pressure and low pressure just like earth - but the actual pressures are much, much less than those encountered on earth.
Since we don't have permanent weather stations scattered around the planet Mars (like we do on earth), it is very hard to predict precisely what type of atmospheric densities a probe will encounter as it travels downwards through the Martian atmosphere. All we will know are the high end and the low end of expected pressures ranges.
Density obviously increases as altitude decreases. But also, density will vary at any given time due to the weather conditions encountered. Mars has changing areas of high pressure and low pressure just like earth - but the actual pressures are much, much less than those encountered on earth.
Since we don't have permanent weather stations scattered around the planet Mars (like we do on earth), it is very hard to predict precisely what type of atmospheric densities a probe will encounter as it travels downwards through the Martian atmosphere. All we will know are the high end and the low end of expected pressures ranges.
marksx said:
OK stupid question time.
When they re talking about varying air density, are they simply referring to the changes due to altitude, or something else?
Air density on Mars is only a 1% of that on Earth. Also the amount of atmosphere (depth & density) an arriving spacecraft encounters during entry can vary by 100% which is why it's so difficult to land safely on Mars.When they re talking about varying air density, are they simply referring to the changes due to altitude, or something else?
FunkyNige said:
jbudgie said:
Is there going to be any sort of live programme for this.
NASA TV will have ithttp://www.nasa.gov/multimedia/nasatv/index.html
August 5, Sunday 11 p.m. - Mars Science Laboratory/Curiosity Rover Landing Coverage of Entry Decent and Landing (Clean Feed with Mission Audio Only) - JPL (Media Channel)
(time is Eastern US time)
Bedazzled said:
Only a couple of days to go... until the red-planet curse strikes once more. Bonkers design, hope they prove me wrong! 
"you may be wondering about the oscillations in these wires... and a million other things".
I am a but curious about the so-called "red planet" curse. I think it is a load of old "media trash" reporting."you may be wondering about the oscillations in these wires... and a million other things".
Trying to soft land items on ANY planet is difficult. Mars has had more probes fired at it than any other planet in the solar system - so you would exopect some of these to fail. It was also a target early on in the space race. The first attempts to launch probes to Mars were in 1960. Failure rates for ALL space missions were very high back then.
In recent years, most Mars probes have been spectacularly successful.
Bedazzled said:
Try telling that to the Russians; 20 missions, zero success. Phobos Grunt being the most recent example, and yet they managed to land a probe on Venus! Overall success rate for Mars missions is about a third, iirc?
The Russians have had poor success with Mars. But NASA and the Europeans have been pretty successful. The only European failure as far as I can recall was the bargain basement UK Beagle 2 - which was only an add-on to an orbiter which has performed magnificently for the past nine years.NASA experienced some failures in the early days of the programme when success in any space endeavour was largely down to luck. They also had a few failures in the 1990s when they tried a "cheaper, faster, lighter" approach - which frankly, wasn't robust enough for the rigours of landing on Mars.
In more recent years, NASA missions to Mars have been extremely successful.
Listed below are all the attempted launches of probes to Mars. As you can see, the Russians have been pretty unsuccessful with the planet - especially with launch failures in the very early days of the space race. The USA has been much more successful. Britain's only Mars probe was made on a shoestring using parts bought from Maplin so its failure was almost guaranteed
Mars 1960A USSR 10 October 1960 flyby failure failed to reach Earth orbit [90]
Mars 1960B USSR 14 October 1960 flyby failure failed to reach Earth orbit [91]
Mars 1962A USSR 24 October 1962 flyby failure exploded in or en route to Earth orbit [92]
Mars 1962B USSR 11 November 1962 (launch) lander failure broke up during transfer to Mars trajectory [93]
Mars 1 USSR 19 June 1963 flyby failure contact lost en route; flew within approximately 193,000 km of Mars [94]
Mariner 3 NASA 5 November 1964 flyby failure protective shield failed to eject, preventing craft from attaining correct trajectory [95]
Zond 2 USSR 6 August 1965 flyby failure contact lost en route; flew within 1,500 km of Mars [96]
Mariner 4 NASA 15 July 1965 flyby success first close-up images of Mars [97]
Mariner 6 NASA 31 July 1969 flyby success [98]
Mariner 7 NASA 5 August 1969 flyby success [99]
Mars 1969A USSR 27 March 1969 orbiter failure launch failure [100]
Mars 1969B USSR 2 April 1969 orbiter failure launch failure [101]
Mariner 8 NASA 9 May 1971 orbiter failure launch vehicle failure [102]
Mariner 9 NASA 14 November 1971 orbiter success first spacecraft to orbit another planet [103]
Mars 2 USSR November 1971 – August 1972 orbiter success first Russian spacecraft to orbit another planet [104]
Mars 2 Lander USSR 27 November 1971 lander and short range rover failure crashed; first manmade object to reach surface of Mars [105]
Mars 3 USSR December 1971 – August 1972 orbiter partial success attained a different orbit than intended due to insufficient fuel [106]
Mars 3 Lander USSR 2 December 1971 lander and short range rover failure contact lost 110 sec after soft landing [107]
Cosmos 419 USSR 10 May 1971 orbiter failure failed to escape Earth orbit [108]
Mars 4 USSR 10 February 1974 orbiter failure orbit insertion failed, became flyby [109]
Mars 5 USSR February 1974 orbiter success [110]
Mars 6 USSR 12 March 1974 flyby success [111]
Mars 6 Lander USSR 12 March 1974 lander failure contact lost 148 sec after parachute deployment (returned 224 seconds of atmospheric data)
Mars 7 USSR 9 March 1974 flyby success [112]
Mars 7 Lander USSR 9 March 1974 lander failure missed Mars
Viking 1 Orbiter NASA June 1976 – August 1980 orbiter success [113]
Viking 1 Lander NASA 20 July 1976 –13 November 1982 lander success first images from surface [114]
Viking 2 Orbiter NASA August 1976 – July 1978 orbiter success [115]
Viking 2 Lander NASA 3 September 1976 –11 April 1980 lander success [116]
Phobos 1 USSR 7 July 1988 (launch) orbiter failure contact lost en route to Mars [117]
Phobos 2 USSR 29 January 1989 – 27 March 1989 orbiter partial success Mars orbit acquired, but contact lost shortly before Phobos approach phase and deployment of Phobos landers [118]
Mars Observer NASA 25 September 1992 (launch) orbiter failure contact lost shortly before Mars orbit insertion [119]
Mars 96 RFSA 16 November 1996 (launch) orbiter failure failed to escape Earth orbit [120]
]
Mars Pathfinder NASA 4 July 1997 –27 September 1997 lander success [125]
Sojourner NASA 6 July 1997 – 27 September 1997 rover success first Mars rover [126]
Mars Global Surveyor NASA 12 September 1997 – 2 November 2006 orbiter success [127]
Mars Climate Orbiter NASA 23 September 1999 orbiter failure Mars orbit insertion failed due to navigation error [128]
Mars Polar Lander NASA 3 December 1999 lander failure contact lost just prior to entering Martian atmosphere [129]
2001 Mars Odyssey NASA 24 October 2001 – orbiter success studying climate and geology; communications relay for Spirit and Opportunity rovers [131]
Nozomi ISAS 14 December 2003 orbiter failure failed to attain Mars orbit, became flyby [132]
Mars Express ESA 25 December 2003 – orbiter success surface imaging and mapping; first European probe in Martian orbit [133]
Beagle 2 UK 25 December 2003 lander failure contact never established after estimated landing [134]
MER-A "Spirit" NASA 4 January 2004 – 22 March 2010 rover success became stuck in May 2009; then operating as a static science station until contact lost in March 2010 [135]
MER-B "Opportunity" NASA 25 January 2004 – rover success [136]
Mars Reconnaissance Orbiter NASA 10 March 2006 – orbiter success surface imaging and surveying [137]
Rosetta ESA 25 February 2007 flyby success gravity assist en route to asteroid and comet encounters [138]
Phoenix NASA 25 May 2008 – 10 November 2008 lander success collection of soil samples near the northern pole to search for water and investigate Mars' geological history and biological potential [139]
Dawn NASA 17 February 2009 flyby success gravity assist en route to Vesta and Ceres [140]
Yinghuo-1 CNSA 8 November 2011 (launch) orbiter failure failed to escape Earth orbit; launched with Fobos-Grunt Phobos lander
MSL Curiosity NASA August 2012 – rover en route to Mars.
Because so many probes have been spectacular successes, it becomes easy to assume that sending these probes vast distances to other worlds is a fairly straightforward task. It is anything but.
Probes miss their targets for all sorts of reasons - loss of communication, failure of a thruster to fire due to mecahnical probelms, failure of on board guidance and even human error - as happened with one US Mars probe when a course correction was forwarded to the probe using the wrong set of numbers (there was a confusion over Metric and Imperial units).
Probes miss their targets for all sorts of reasons - loss of communication, failure of a thruster to fire due to mecahnical probelms, failure of on board guidance and even human error - as happened with one US Mars probe when a course correction was forwarded to the probe using the wrong set of numbers (there was a confusion over Metric and Imperial units).
Gassing Station | Science! | Top of Page | What's New | My Stuff