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A cleaning event is a phenomenon whereby
dust
Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...
is removed from
solar panel
A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a photo ...
s, in the context of exploration and science rovers on
Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...
, supposedly by the action of
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
. The term cleaning event is used on several
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
webpages; generally supposing that Martian winds have blown dust clear off the probes on Mars, including the solar panels which power them, increasing their energy output. The nature of the cleaning events is not known, but the assumption is that wind blows the dust off the panels.
Cleaning events were discovered in 2004 when several times power levels increased by 5% overnight, in contrast to the expectation they would decreasethe added power allowed the missions to continue beyond their expected lifetime.
One theory is that wind currents in craters aid in cleaning events, and also if the rover is sloped, this is speculated to help remove dust.
The term started being used in 2004 as the
Mars Exploration Rovers
NASA's Mars Exploration Rover (MER) mission was a robotic space mission involving two Mars rovers, ''Spirit'' and ''Opportunity'', exploring the planet Mars. It began in 2003 with the launch of the two rovers to explore the Martian surface and ...
' (MER) solar panels started to benefit from these events.
The rovers were expected to last about 90
sols (Martian days) on Mars, after which dust would cover their solar panels and reduce solar power to levels too low for the rovers to operate. However, power levels went back up due to the cleaning events caused by the winds in the Martian atmosphere. Periodic cleaning events have allowed the MERs to operate far longer than the planned 3 months. The ''
Spirit
Spirit or spirits may refer to:
Liquor and other volatile liquids
* Spirits, a.k.a. liquor, distilled alcoholic drinks
* Spirit or tincture, an extract of plant or animal material dissolved in ethanol
* Volatile (especially flammable) liquids, ...
'' rover finally ceased operation in early 2010, and the ''
Opportunity
Opportunity may refer to:
Places
* Opportunity, Montana, an unincorporated community, United States
* Opportunity, Nebraska, an unincorporated community, United States
* Opportunity, Washington, a former census-designated place, United States
* 3 ...
'' rover remained active until mid 2018, more than 14 years after landing.
Cleaning events can either be
rapid
Rapids are sections of a river where the river bed has a relatively steep gradient, causing an increase in water velocity and turbulence.
Rapids are hydrological features between a ''run'' (a smoothly flowing part of a stream) and a ''cascade''. ...
, such as overnight, or over many days where solar power slowly goes up. For example, with the MER-A ''Spirit'' rover, on 18 and 28 April 2009, the power output of the solar arrays was increased by cleaning events.
The power output of ''Spirit's'' solar arrays increased from 223 watt-hours per day on 31 March 2009 to 372 watt-hours per day on 29 April 2009.
''Spirit'' had experienced multiple cleaning events during its operation that aided in its mission extension. However, the lack of cleaning events was noted as a factor in its demise.
Other factors that affect solar power output include the
opacity of the
Martian atmosphere
The atmosphere of Mars is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.8%), and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and no ...
and Martian seasonal changes; however, this does not account for the directly observable removal of dust from the upper surfaces of the rovers as shown in the images.
The
Materials Adherence Experiment
The Materials Adherence Experiment (MAE) was a material science experiment conducted between July 4, 1997 and August 12, 1997 during NASA's ''Mars Pathfinder'' mission. This was a joint experiment between NASA and the Jet Propulsion Laboratory ...
had a glass plate that allowed the dust to be cleared off and protected a
Gallium arsenide
Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a Zincblende (crystal structure), zinc blende crystal structure.
Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monoli ...
photo-cell. It was part of the
Mars Pathfinder
''Mars Pathfinder'' (''MESUR Pathfinder'') is an American robotic spacecraft that landed a base station with a roving probe on Mars in 1997. It consisted of a lander, renamed the Carl Sagan Memorial Station, and a lightweight, wheeled robot ...
program in the 1990s. This allowed the rate at which dust accumulated to be measured.
Noted cleaning events
*In early 2014 cleaning events boosted power levels on the ''Opportunity'' (MER-B) rover by 70%.
A particularly strong cleaning event occurred in March 2014 while the rover was at
Endeavour crater
Endeavour is an impact crater located in the Meridiani Planum extraterrestrial plain within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. Endeavour is about in diameter. Using ''Mars Reconnaissance Orbiter'' data, phy ...
.
See also
*
Atmosphere of Mars
The atmosphere of Mars is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.8%), and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and no ...
*
''Curiosity'' rover
*
Exploration of Mars
The planet Mars has been explored remotely by spacecraft. Probes sent from Earth, beginning in the late 20th century, have yielded a large increase in knowledge about the Martian system, focused primarily on understanding its geology and habit ...
*
MER Mars Exploration Rover mission
*
MER-A ''Spirit'' rover
*
MER-B ''Opportunity'' rover
*
Solar panel
A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a photo ...
References
External links
"PIA07492: Before and After a Cleaning Event on ''Spirit''", JPL/NASA
{{DEFAULTSORT:Cleaning Event
Mars Exploration Rover mission
Solar power and space