Editing Mars Pathfinder (section)

==Rover operations==
{{further|Sojourner (rover)}}

===''Sojourner'' deployment===
The ''Sojourner'' rover departed from the lander on Sol 2, after its landing on July 4, 1997. As the next sols progressed it approached some rocks, which the scientists named "[[Barnacle Bill (Mars)|Barnacle Bill]]", "[[Yogi Rock|Yogi]]", and "[[Scooby-Doo]]", after famous [[cartoon]] characters. The rover made measurements of the elements found in those rocks and in the martian soil, while the lander took pictures of the ''Sojourner'' and the surrounding terrain, in addition to making climate observations.

The ''Sojourner'' is a six-wheeled, {{cvt|65|cm|in|adj=on}} long vehicle, {{cvt|48|cm|in}} wide, {{cvt|30|cm|in}} tall and weighing {{cvt|10.5|kg|lb}}.<ref>{{Cite web |url=http://mepag.jpl.nasa.gov/meeting/mar-09/02_MEPAG_McCuistion_Mar_09.pdf |title=Mars – the search for life |date=March 4, 2009 |access-date=March 28, 2009 |publisher=NASA |archive-url=https://web.archive.org/web/20090327083233/http://mepag.jpl.nasa.gov/meeting/mar-09/02_MEPAG_McCuistion_Mar_09.pdf |archive-date=March 27, 2009 |url-status=dead }}</ref> Its maximum speed reached {{cvt|1|cm/s|in/s}}. ''Sojourner'' travelled approximately {{cvt|100|m|ft}} in total, never more than {{cvt|12|m|ft}} from the ''Pathfinder'' station. During its 83 [[Timekeeping on Mars#Sols|sols]] of operation, it sent 550 photographs to Earth and analyzed the [[chemistry|chemical]] properties of 16 locations near the lander. (See also [[Rover (space exploration)|Space exploration rovers]])

===''Sojourner''{{'}}s rock analysis===
[[File:Sojourner and Barnacle Bill.jpg|thumb|''Sojourner'' next to the rock [[Barnacle Bill (Mars)|Barnacle Bill]]]]
The first analysis on a rock started on Sol 3 with Barnacle Bill. The [[APXS|Alpha Particle X-ray Spectrometer]] (APXS) was used to determine its composition, the spectrometer taking ten hours to make a full scan of the sample. It found all the elements except [[hydrogen]], which constitutes just 0.1 percent of the rock's or soil's mass.

The APXS works by irradiating rocks and soil samples with [[alpha particle]]s ([[helium]] [[atomic nucleus|nuclei]], which consist of two [[proton]]s and two [[neutron]]s). The results indicated that "Barnacle Bill" is much like Earth's [[andesite]]s, confirming past [[volcano|volcanic]] activity.  The discovery of andesites shows that some Martian rocks have been remelted and reprocessed.  On Earth, andesite forms when magma sits in pockets of rock while some of the iron and magnesium settle out.  Consequently, the final rock contains less iron and magnesiums and more silica.  Volcanic rocks are usually classified by comparing the relative amount of alkalis (Na<sub>2</sub>O and K<sub>2</sub>O) with the amount of silica (SiO<sub>2</sub>).  Andesite is different from the rocks found in meteorites that have come from Mars.<ref name="Golombek, M 1997"/><ref name="nssdc.gsfc.nasa.gov">{{cite web |url=http://nssdc.gsfc.nasa.gov/planetary/marspath/apxs.html |title=APXS Composition Results |work=NASA |access-date=June 10, 2015 |archive-url=https://web.archive.org/web/20160603120939/http://nssdc.gsfc.nasa.gov/planetary/marspath/apxs.html |archive-date=June 3, 2016 |url-status=live }}</ref><ref name="Bruckner, J. 2001">{{cite journal |last1=Bruckner |first1=J. |first2=G. |last2=Dreibus |first3=R. |last3=Rieder |first4=H. |last4=Wanke |year=2001 |title=Revised Data of the Mars Pathfinder Alpha Proton X-ray spectrometer: Geochemical Behavior of Major and Minor Elements |journal=Lunar and Planetary Science XXXII|page=1293 |bibcode=2001LPI....32.1293B }}</ref>

Analysis of the Yogi rock again using the APXS showed that it was a [[basalt]]ic rock, more primitive than Barnacle Bill. Yogi's shape and texture show that it was probably deposited there by a [[flood]].

Another rock, named Moe, was found to have certain marks on its surface, demonstrating erosion caused by the wind. Most rocks analyzed showed a high content of [[silicon]]. In another region known as Rock Garden, ''Sojourner'' encountered crescent moon-shaped dunes, which are similar to [[dunes|crescentic dunes]] on Earth.

By the time that final results of the mission were described in a series of articles in the journal ''Science'' (December 5, 1997), it was believed that the rock Yogi contained a coating of dust, but was similar to the rock Barnacle Bill.  Calculations suggest that the two rocks contain mostly the minerals orthopyroxene (magnesium-iron silicate), feldspars (aluminum silicates of potassium, sodium, and calcium), and quartz (silicon dioxide), with smaller amounts of magnetite, ilmenite, iron sulfide, and calcium phosphate.<ref name="Golombek, M 1997"/><ref name="nssdc.gsfc.nasa.gov"/><ref name="Bruckner, J. 2001"/>
{{Wide image|PIA01153.jpg|1200px|Annotated panorama of [[Rock (geology)|rocks]] near the [[Sojourner (rover)|''Sojourner'' rover]] (December 5, 1997)}}

===On-board computer===
{{See also|Comparison of embedded computer systems on board the Mars rovers}}

The [[embedded system|embedded]] computer on board the ''Sojourner'' rover was based around the 2&nbsp;MHz<ref>{{cite web |url=http://mars.jpl.nasa.gov/MPF/rover/faqs_sojourner.html#cpu |title=Mars Pathfinder FAQs - Sojourner CPU |work=NASA |access-date=June 10, 2015 |archive-url=https://web.archive.org/web/20141229132636/http://mars.jpl.nasa.gov/MPF/rover/faqs_sojourner.html#cpu |archive-date=December 29, 2014 |url-status=live }}</ref> [[Intel 80C85]] [[Central processing unit|CPU]] with 512&nbsp;[[Kilobyte|KB]] of [[Random access memory|RAM]] and 176&nbsp;KB of [[flash memory]] [[solid state disk|solid-state]] [[Data storage device|storage]], running a [[cyclic executive]].<ref name="ieeecomputer">{{cite journal |first1=Max |last1=Bajracharya |first2=Mark W. |last2=Maimone |first3=Daniel |last3=Helmick |title=Autonomy for Mars rovers: past, present, and future |journal=[[Computer (journal)|Computer]] |publisher=[[IEEE Computer Society]] |date=December 2008 |volume=41 |number=12 |pages=44–50 |doi=10.1109/MC.2008.479 |s2cid=9666797 |issn=0018-9162 |url=http://users.etown.edu/w/wunderjt/ITALY_2009/PUBLICATION_MARS_SPIRIT_ALL_PATH_PLANNING_JPL.pdf |access-date=June 10, 2015 |archive-url=https://web.archive.org/web/20160304095252/http://users.etown.edu/w/wunderjt/ITALY_2009/PUBLICATION_MARS_SPIRIT_ALL_PATH_PLANNING_JPL.pdf |archive-date=March 4, 2016 |url-status=live }}</ref>

The computer of the ''Pathfinder'' lander was a [[IBM RAD6000|Radiation Hardened IBM Risc 6000]] Single Chip (Rad6000 SC) [[Central processing unit|CPU]] with 128&nbsp;MB of RAM and 6&nbsp;MB of [[EEPROM]]<ref>{{cite web | url=http://quest.arc.nasa.gov/mars/ask/about-mars-path/pathfinder_computer.txt | title="QUESTION: What type of computer is the Pathfinder utilizing? ..." (NASA Quest Q&A) | date=1997 | access-date=July 21, 2015 | publisher=[[NASA]] | archive-url=https://web.archive.org/web/20160307043527/http://quest.arc.nasa.gov/mars/ask/about-mars-path/pathfinder_computer.txt | archive-date=March 7, 2016 | url-status=dead }}</ref><ref>{{cite web | url=http://quest.arc.nasa.gov/mars/ask/about-rover/Why_to_use_a_80C85_microprocessor_in_Rover_.txt | title="QUESTION: When it was designed, why was only a single 80C85 CPU used? ..." (NASA Quest Q&A) | date=1997 | access-date=July 21, 2015 | publisher=[[NASA]] | archive-url=https://web.archive.org/web/20150723003545/http://quest.arc.nasa.gov/mars/ask/about-rover/Why_to_use_a_80C85_microprocessor_in_Rover_.txt | archive-date=July 23, 2015 | url-status=dead }}</ref> and its [[operating system]] was [[VxWorks]].<ref name=Wind_River>{{cite web | url=http://www.windriver.com/news/press/pr.html?ID=314 | title=Wind River Powers Mars Exploration Rovers—Continues Legacy as Technology Provider for NASA's Space Exploration | date=June 6, 2003 | access-date=August 28, 2009 | publisher=[[Wind River Systems]] | archive-url=https://web.archive.org/web/20100106090354/http://www.windriver.com/news/press/pr.html?ID=314 | archive-date=January 6, 2010 | url-status=live }}</ref>

The mission was jeopardised by a [[Concurrent computing|concurrent]] software bug in the lander,<ref>Parallel sparking: Many chips make light work, Douglas Heaven, ''New Scientist'' magazine, issue 2930, August 19, 2013, p44. [https://www.newscientist.com/article/mg21929301.000-parallel-sparking-many-chips-make-light-work.html?page=2 Online (by subscription)] {{Webarchive|url=https://web.archive.org/web/20141006101728/http://www.newscientist.com/article/mg21929301.000-parallel-sparking-many-chips-make-light-work.html?page=2 |date=October 6, 2014 }}</ref> which had been found in preflight testing but was deemed a glitch and therefore given a low priority as it only occurred in certain unanticipated heavy-load conditions, and the focus was on verifying the entry and landing code. The problem, which was reproduced and corrected from Earth using a laboratory duplicate thanks to the logging and debugging functionality enabled in the flight software, was due to [[Reset (computing)|computer resets]] caused by [[priority inversion]]. No scientific or engineering data was lost after a computer reset, but all the following operations were interrupted until the next day.<ref>{{cite web |url=http://research.microsoft.com/en-us/um/people/mbj/Mars_Pathfinder/Authoritative_Account.html |title=What really happened on Mars? – Authoritative Account |first=Glenn E. |last=Reeves |work=Microsoft.com |date=December 15, 1997 |access-date=June 10, 2015 |archive-url=https://web.archive.org/web/20150611035733/http://research.microsoft.com/en-us/um/people/mbj/mars_pathfinder/authoritative_account.html |archive-date=June 11, 2015 |url-status=live }}</ref><ref>{{cite web |url=http://research.microsoft.com/en-us/um/people/mbj/Mars_Pathfinder/ |title=What really happened on Mars? |first=Michael B. |last=Jones |work=Microsoft.com |date=December 16, 1997 |access-date=June 10, 2015 |archive-url=https://web.archive.org/web/20150612010836/http://research.microsoft.com/en-us/um/people/mbj/mars_pathfinder/ |archive-date=June 12, 2015 |url-status=live }}</ref> Four resets occurred (on July 5, 10, 11 and 14) during the mission,<ref>{{cite web|url= http://www.oarval.org/missionsr2.htm|title= The Mars Pathfinder Mission Status Reports &mdash; Second Week|publisher= Office of the Flight Operations Manager &ndash; Mars Pathfinder Project|access-date= October 24, 2015|archive-url= https://web.archive.org/web/20160104210211/http://www.oarval.org/missionsr2.htm|archive-date= January 4, 2016|url-status= live}}</ref> before patching the software on July 21 to enable [[priority inheritance]].<ref>{{cite web|url= http://www.oarval.org/missionsr3.htm|title= The Mars Pathfinder Mission Status Reports &mdash; Third Week|publisher= Office of the Flight Operations Manager &ndash; Mars Pathfinder Project|access-date= October 24, 2015|archive-url= https://web.archive.org/web/20160410091935/http://www.oarval.org/missionsr3.htm|archive-date= April 10, 2016|url-status= live}}</ref>