# Why does the Mars Spirit Rover have an expected lifetime of 90 days?

**URL:** <https://boards.straightdope.com/t/why-does-the-mars-spirit-rover-have-an-expected-lifetime-of-90-days/224999>\
**Category:** Factual Questions\
**Created:** [January 17, 2004, 9:38pm UTC](https://boards.straightdope.com/t/why-does-the-mars-spirit-rover-have-an-expected-lifetime-of-90-days/224999 "2004-01-17T21:38:00Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![RickJay](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@RickJay](https://boards.straightdope.com/u/RickJay)\
**Post date:** [January 20, 2004, 8:30pm UTC](https://boards.straightdope.com/t/why-does-the-mars-spirit-rover-have-an-expected-lifetime-of-90-days/224999/21 "2004-01-20T20:30:20Z")

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> [@Cervaise](#):
>
> The astronauts who went to the moon took quite a few rads in the process. I read somewhere, though I don’t remember where so I can’t dig up a cite quickly, that the lunar explorers have shown a somewhat elevated rate of cancer. However, since there’s fewer than twenty of them, it’s not really an epidemiologically reliable sample.

There were 24 Apollo astronauts who actually flew all the way to the Moon:

Jim Lovell  
William Anders  
Frank Borman  
Thomas Stafford  
John Young  
Gene Cernan  
Neil Armstrong  
Buzz Aldrin  
Michael Collins  
Charles Conrad  
Richard Gordon  
Alan Bean  
John Swigert, whose Bacon number is 0  
Fred Haise  
Alan Shepard  
Stuart Roosa  
Edgar Mitchell  
David Scott  
Alfred Worden  
James Irwin  
Tom Mattingly  
Charlie Duke  
Ronald Evans  
Harry Schmitt

Lovell, Young, and Cernan went twice.

Of those, two are dead of cancer. Not unusual given that most of these men are pretty old now, although Swigert died young.

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**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\
**Post date:** [January 21, 2004, 2:21am UTC](https://boards.straightdope.com/t/why-does-the-mars-spirit-rover-have-an-expected-lifetime-of-90-days/224999/22 "2004-01-21T02:21:13Z")

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**Clayton\_e:** No prob. Here’s your link: [Mars Science Laboratory Mission](http://centauri.larc.nasa.gov/msl/)

The landing technique is interesting for this one, and quite ingenious. A series of parachutes slows it down just like the Spirit rover, but instead of being dropped in an airbag, the descent engine hovers over the ground and lowers the rover on a cable. When the rover touches down, it cuts the cable, and the descent stage flies away and then crashes some distance from the rover.

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