Sinus Meridiani

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Sinus Meridiani
Mars telescope.jpg
Sinus Meridiani, seen as the dark region just below the centre of the image at the end of the protrusion from the left (Sinus Sabaeus)
Coordinates 0°N0°E / 0°N 0°E / 0; 0 Coordinates: 0°N0°E / 0°N 0°E / 0; 0
EponymMeridian Bay

Sinus Meridiani (Latin Sinus meridiani, "Meridian Bay") is an albedo feature on Mars stretching east-west just south of the planet's equator. It was named by the French astronomer Camille Flammarion in the late 1870s.

Contents

In 1979-2001, the vicinity of this feature (with size about 1,600 kilometers (990 mi) and coordinates of the center 7°07′S4°00′E / 7.12°S 4°E / -7.12; 4 ) was named Terra Meridiani. [1]

Observational history

This image shows an arcuate ridge in Terra Meridiani. Curvilinear Ridge in Terra Meridiani.jpg
This image shows an arcuate ridge in Terra Meridiani.
Enigmatic ridges in Terra Meridiani from HiRISE, 2012. Terra Meridiani is one of the more complex regions on Mars. Ridges in Terra Meridiani HiRISE.jpg
Enigmatic ridges in Terra Meridiani from HiRISE, 2012. Terra Meridiani is one of the more complex regions on Mars.

The name Sinus Meridiani was given to a classic albedo feature on Mars by the French astronomer Camille Flammarion in the late 1870s. Prior astronomers, notably the German team of Wilhelm Beer and Johann Heinrich von Mädler and then the Italian Giovanni Schiaparelli, had chosen a particular point on Mars as being the location of its prime meridian when they charted their observations. Accepting suggestions that dark areas on the surface of Mars were seas or oceans, Flammarion named a dark area at that point "Sinus Meridiani," literally "Meridian Bay," when he worked on his compilation and analysis of all prior observations of Mars. In 1958, this name was approved by International Astronomical Union. [2]

Since the 1960s, when flybys and access to orbital spacecraft imagery of Mars began to become commonplace, many relief features were named in addition to previously named albedo features. In 1979, a region of Sinus Meridiani was named Terra Meridiani, literally "Meridian Land." In 2001, boundaries of regional features were redefined, and this name was dropped. [1]

Meridiani Planum

The name Meridiani Planum , literally "Meridian Plain," is used to refer specifically to the landing site of Mars Exploration Rover Opportunity , in the western portion of Sinus Meridiani. This site was chosen by the Mars Exploration Rover team both for its characteristic as a flat and mostly rock-free plain (and hence a safe landing site), and also as a site which showed the spectral signature of the mineral hematite, which is often a sign of deposition in an aqueous environment.

Analysis by Opportunity

The rock "Berry Bowl." Xpe pubeng approved 032304 color berry bowl-B060R1 br.jpg
The rock "Berry Bowl."
This image, taken by the microscopic imager, reveals shiny, spherical objects embedded within the trench wall The Mystery of the Sparkling Spheres.jpg
This image, taken by the microscopic imager, reveals shiny, spherical objects embedded within the trench wall
"Blueberries" (hematite spheres) on a rocky outcrop at Eagle Crater. Note the merged triplet in the upper left. Blueberries eagle.gif
"Blueberries" (hematite spheres) on a rocky outcrop at Eagle Crater. Note the merged triplet in the upper left.

The Opportunity rover found that the soil at Meridiani Planum was very similar to the soil at Gusev crater and Ares Vallis; however, in many places at Sinus Meridiani, the soil was covered with round, hard, gray spherules, dubbed "blueberries." [3] These blueberries were found to be composed almost entirely of the mineral hematite. It was decided that the spectra signal spotted from orbit by 2001 Mars Odyssey was produced by these spherules. Further studies found that the blueberries were concretions formed in the ground by water. [4] Over time, these concretions weathered from what was overlying rock, and then became concentrated on the surface as a lag deposit. The concentration of spherules in bedrock could have produced the observed blueberry covering from the weathering of as little as one meter of rock. [5] [6] Most of the soil consisted of olivine basalt sands that did not come from the local rocks, and is thus speculated to have come from elsewhere. [7]

Minerals in dust

A Mössbauer spectrum was made of the dust that gathered on Opportunity's capture magnet. The results suggested that the magnetic component of the dust was titanomagnetite, rather than just plain magnetite, as was once thought. Trace amounts of olivine were also detected, which indicated a long arid period on the planet. On the other hand, a small amount of hematite that was present meant that there may have been liquid water for a short time in the early history of the planet. [8] Because the Rock Abrasion Tool (RAT) found it easy to grind into the bedrocks, it is thought that the rocks are much softer than the rocks at Gusev crater.

Bedrock minerals

"Homestake" formation PIA15034 Pancam sol2769 L257F.tif
"Homestake" formation

Few rocks were visible on the surface where Opportunity landed, but bedrock that was exposed in craters was examined by the suite of instruments on the Rover. [9] Bedrock rocks were found to be sedimentary rocks with a high concentration of sulfur in the form of calcium and magnesium sulfates. Some of the sulfates that may be present in bedrocks are kieserite, sulfate anhydrate, bassanite, hexahydrite, epsomite, and gypsum. Salts, such as halite, bischofite, antarcticite, blödite, vanthoffite, or glauberite may also be present. [10] [11]

The rocks contained the sulfates had a light tone compared to isolated rocks and rocks examined by landers/rovers at other locations on Mars. The spectra of these light toned rocks, containing hydrated sulfates, were similar to spectra taken by the Thermal Emission Spectrometer on board the Mars Global Surveyor. The same spectrum is found over a large area, so it is believed that water once appeared over a wide region, not just in the area explored by Opportunity. [12]

The Alpha particle X-ray spectrometer (APXS) found rather high levels of phosphorus in the rocks. Similar high levels were found by other rovers at Ares Vallis and Gusev crater, so it has been hypothesized that the mantle of Mars may be phosphorus-rich. [13] The minerals in the rocks could have originated by acid weathering of basalt. Because the solubility of phosphorus is related to the solubility of uranium, thorium, and rare-earth elements, they are all also expected to be enriched in rocks. [14]

When Opportunity traveled to the rim of the impact crater Endeavour, it found a white vein that was later identified as being pure gypsum. [15] [16] It was formed when water was discovered to harbor a then-unknown gypsum formation, at the time dubbed "Homestake," deposited the mineral into a crack in the rock.

Evidence for water

Cross-bedding features in rock "Last Chance" LastChance D JG03-B058R1 br.jpg
Cross-bedding features in rock "Last Chance"

Examination of bedrocks in Sinus Meridiani showed evidence of the mineral jarosite, which forms only in water. This discovery proved that water once existed in Sinus Meridiani [17] In addition, some rocks showed small laminations with shapes only created by gently flowing water. [18] The first such laminations were found in a rock called "The Dells." Geologists would say that the cross-stratification showed festoon geometry from transport in subaqueous ripples. [19]

Box-shaped holes in some rocks were caused by sulfates forming large crystals, and then when the crystals later dissolved, holes, called vugs, were left behind. [20] The concentration of the element bromine in rocks was highly variable probably because it is very soluble. Water may have concentrated it in places before it evaporated. Another mechanism for concentrating highly soluble bromine compounds is frost deposition, which, at night, would form very thin films of water that would concentrate bromine in certain spots. [21]

Rock from impact

One rock, dubbed "Bounce Rock," was discovered sitting on the sandy plains. It was later found to be ejecta from an impact crater, known as tektites. Its chemistry was different from the bedrock's. Containing mostly pyroxene and plagioclase with no olivine, it closely resembled a part, Lithology B, of the shergottite meteorite EETA 79001, a meteorite known to have come from Mars. Bounce rock received its name by being near an airbag bounce mark. [5]

Meteorites

Opportunity found multiple meteorites on the plains of Sinus Meridiani. The first one analyzed with Opportunity's instruments was named "Heatshield Rock," as it was found near where Opportunity's headshield landed. Examination with the Miniature Thermal Emission Spectrometer (Mini-TES), Mossbauer spectrometer, and APXS, lead researchers to classify it as an IAB meteorite. The APXS determined it was composed of 93% iron and 7% nickel. The cobble named "Fig Tree Barberton" is thought to be a stony or stony-iron meteorite (mesosiderite silicate), [22] [23] while "Allan Hills" and "Zhong Shan" may be iron meteorites.

Geological history

Observations at the site have led scientists to believe that the area was flooded with water a number of times and was subjected to evaporation and desiccation. [5] In the process, sulfates were deposited. After sulfates cemented the sediments, hematite concretions grew by precipitation from groundwater. Some sulfates formed into large crystals, which later dissolved to leave vugs. Several lines of evidence point toward an arid climate in the past billion years or so, but a climate supporting water, at least for a time, in the distant past. [24]

See also

Related Research Articles

Mars Exploration Rover NASA mission to explore Mars via two rovers (Spirit and Opportunity); launched in 2003

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Gusev (Martian crater)

Gusev is a crater on the planet Mars and is located at 14.5°S 175.4°E and is in the Aeolis quadrangle. The crater is about 166 kilometers in diameter and formed approximately three to four billion years ago. It was named after Russian astronomer Matvey Gusev (1826–1866) in 1976.

Meridiani Planum

Meridiani Planum is a plain located 2 degrees south of Mars's equator, in the westernmost portion of Sinus Meridiani. It hosts a rare occurrence of gray crystalline hematite. On Earth, hematite is often formed in hot springs or in standing pools of water; therefore, many scientists believe that the hematite at Meridiani Planum may be indicative of ancient hot springs or that the environment contained liquid water. The hematite is part of a layered sedimentary rock formation about 200 to 800 meters thick. Other features of Meridiani Planum include volcanic basalt and impact craters.

Endurance (crater)

Endurance is an impact crater lying situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. This crater was visited by the Opportunity rover from May until December 2004. Mission scientists named the crater after the ship Endurance that sailed to the Antarctic through the Weddell Sea during the ill-fated 1914-1917 Imperial Trans-Antarctic Expedition, considered to be the last expedition of the Heroic Age of Antarctic Exploration organized by Ernest Shackleton.

Eagle (Meridiani Planum crater)

Eagle is a 22-metre long impact crater located on the Meridiani Planum extraterrestrial plain, situated within the Margaritifer Sinus quadrangle (MC-19) portion of the planet Mars. The Opportunity rover came to rest inside Eagle crater when it landed in 2004. Scientists were delighted that the rover landed there, as the crater contains rocky outcroppings that helped prove that Meridiani was once an ocean floor.

Fram (crater)

Fram is an impact crater located within the Meridiani Planum extraterrestrial plain, situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. It was visited by the rover Opportunity (MER-B) on Sol 84, April 24, 2004.

Martian spherules

Martian spherules are the abundant spherical hematite inclusions discovered by the Mars rover Opportunity at Meridiani Planum on the planet Mars in 2004.

Columbia Hills (Mars) Range of low hills inside Gusev crater on Mars

The Columbia Hills are a range of low hills inside Gusev crater on Mars. They were observed by the Mars Exploration Rover Spirit when it landed within the crater in 2004. They were promptly given an unofficial name by NASA since they were the most striking nearby feature on the surface. The hills lie approximately 3 kilometres (1.9 mi) away from the rover's original landing position. The range is named to memorialize the Space Shuttle Columbia disaster. On February 2, 2004, the individual peaks of the Columbia Hills were named after the seven astronauts who died in the disaster. Spirit spent a few years exploring the Columbia Hills until it ceased to function in 2010. It was also considered a potential landing site for the Mars 2020 Perseverance rover, before the selection of Jezero crater in November 2018.

Heat Shield Rock Basketball-sized iron-nickel meteorite found on Mars

Heat Shield Rock is a basketball-sized iron-nickel meteorite found on the Meridiani Planum plain of Mars by the Mars rover Opportunity in January 2005.

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Bounce Rock Football-sized primarily pyroxene rock found in the Margaritifer Sinus quadrangle of Mars

Bounce Rock is a football-sized primarily pyroxene rock found within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. It was discovered and observed by the Mars Exploration Rover Opportunity in April 2004. The rock was named for it having been struck by Opportunity as the craft bounced to a stop during its landing stage.

Lunae Palus quadrangle Quadrangle map of Mars

The Lunae Palus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is also referred to as MC-10. Lunae Planum and parts of Xanthe Terra and Chryse Planitia are found in the Lunae Palus quadrangle. The Lunae Palus quadrangle contains many ancient river valleys.

Margaritifer Sinus quadrangle One of a series of 30 quadrangle maps of Mars

The Margaritifer Sinus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Margaritifer Sinus quadrangle is also referred to as MC-19. The Margaritifer Sinus quadrangle covers the area from 0° to 45° west longitude and 0° to 30° south latitude on Mars. Margaritifer Sinus quadrangle contains Margaritifer Terra and parts of Xanthe Terra, Noachis Terra, Arabia Terra, and Meridiani Planum.

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 22 kilometers (14 mi) in diameter. Using Mars Reconnaissance Orbiter data, phyllosilicate-bearing outcrops have been detected along its rim. These minerals may have formed under wet conditions in a low-acidic environment during the early history of Mars. There are raised rim segments to the north, east, and southwest. The rim has become worn, rounded and degraded, with infilling of plains material in a manner similar to the Victoria crater.

Henry (Martian crater) Martian crater

Henry is a large crater in the Arabia quadrangle of Mars. It is 171 kilometres (106 mi) in diameter and was named after the brothers Paul Henry and Prosper Henry, both of whom were French telescope makers and astronomers.

The mineralogy of Mars is the chemical composition of rocks and soil that encompass the surface of Mars. Various orbital crafts have used spectroscopic methods to identify the signature of some minerals. The planetary landers performed concrete chemical analysis of the soil in rocks to further identify and confirm the presence of other minerals. The only samples of Martian rocks that are on Earth are in the form of meteorites. The elemental and atmospheric composition along with planetary conditions is essential in knowing what minerals can be formed from these base parts.

Mars may contain ores that would be very useful to potential colonists. The abundance of volcanic features together with widespread cratering are strong evidence for a variety of ores. While nothing may be found on Mars that would justify the high cost of transport to Earth, the more ores that future colonists can obtain from Mars, the easier it would be to build colonies there.

Groundwater on Mars Water held in permeable ground

During past ages, there was rain and snow on Mars; especially in the Noachian and early Hesperian epochs. Some moisture entered the ground and formed aquifers. That is, the water went into the ground, seeped down until it reached a formation that would not allow it to penetrate further. Water then accumulated forming a saturated layer. Deep aquifers may still exist.

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Timeline of <i>Opportunity</i> Robotic rover that was active on the planet Mars from 2004 to 2018

Opportunity is a robotic rover that was active on the planet Mars from 2004 to 2018. Launched on July 7, 2003, Opportunity landed on Mars' Meridiani Planum on January 25, 2004 at 05:05 Ground UTC, three weeks after its twin Spirit (MER-A), also part of NASA's Mars Exploration Rover Mission, touched down on the other side of the planet. While Spirit became immobile in 2009 and ceased communications in 2010, Opportunity exceeded its planned 90 sol duration of activity by 17 years, 287 days. Opportunity continued to move, gather scientific observations, and report back to Earth until 2018. What follows is a summary of events during its continuing mission.

References

  1. 1 2 "Terra Meridiani". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
  2. ↑ "Sinus Meridiani". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
  3. ↑ Yen, A., et al. 2005. An integrated view of the chemistry and mineralogy of martian soils. Nature. 435.: 49-54.
  4. ↑ Bell, J (ed.) The Martian Surface. 2008. Cambridge University Press. ISBN   978-0-521-86698-9
  5. 1 2 3 Squyres, S. et al. 2004. The Opportunity Rover’s Athena Science Investigation at Meridiani Planum, Mars. Science: 1698-1703.
  6. ↑ Soderblom, L., et al. 2004. Soils of Eagle Crater and Meridiani Planum at the Opportunity Rover Landing Site. Science: 306. 1723-1726.
  7. ↑ Christensen, P., et al. Mineralogy at Meridiani Planum from the Mini-TES Experiment on the Opportunity Rover. Science: 306. 1733-1739.
  8. ↑ Goetz, W., et al. 2005. Indication of drier periods on Mars from the chemistry and mineralogy of atmospheric dust. Nature: 436.62-65.
  9. ↑ Bell, J., et al. 2004. Pancam Multispectral Imaging Results from the Opportunity Rover at Meridiani Planum. Science: 306.1703-1708.
  10. ↑ Christensen, P., et al. 2004 Mineralogy at Meridiani Planum from the Mini-TES Experiment on the Opportunity Rover. Science: 306. 1733-1739.
  11. ↑ Squyres, S. et al. 2004. In Situ Evidence for an Ancient Aqueous Environment at Meridian Planum, Mars. Science: 306. 1709-1714.
  12. ↑ Hynek, B. 2004. Implications for hydrologic processes on Mars from extensive bedrock outcrops throughout Terra Meridiani. Nature: 431. 156-159.
  13. ↑ Dreibus,G. and H. Wanke. 1987. Volatiles on Earth and Marsw: a comparison. Icarus. 71:225-240
  14. ↑ Rieder, R., et al. 2004. Chemistry of Rocks and Soils at Meridiani Planum from the Alpha Particle X-ray Spectrometer. Science. 306. 1746-1749
  15. ↑ "NASA - NASA Mars Rover Finds Mineral Vein Deposited by Water". www.nasa.gov.
  16. ↑ "Durable NASA rover beginning ninth year of Mars work". sciencedaily.com.
  17. ↑ Klingelhofer, G. et al. 2004. Jarosite and Hematite at Meridiani Planum from Opportunity’s Mossbauer Spectrometer. Science: 306. 1740–1745.
  18. ↑ Herkenhoff, K., et al. 2004. Evidence from Opportunity’s Microscopic Imager for Water on Meridian Planum. Science: 306. 1727-1730
  19. ↑ Squyres, S. et al. 2004. In Situ Evidence for an Ancient Aqueous Environment at Meridian Planum, Mars. Science: 306. 1709-1714.
  20. ↑ Herkenhoff, K., et al 2004 Evidence from Opportunity's Microscopic Imager for Water on Meridian Planum. Science: 306. 1727–1730
  21. ↑ Yen, A., et al. 2005. An integrated view of the chemistry and mineralogy of martian soils. Nature. 435.: 49-54.
  22. ↑ Squyres, S., et al. 2009. Exploration of Victoria Crater by the Mars Rover Opportunity. Science: 1058-1061.
  23. ↑ Schroder,C., et al. 2008. J. Geophys. Res.: 113.
  24. ↑ Clark, B. et al. Chemistry and mineralogy of outcrops at Meridiani Planum. Earth Planet. Sci. Lett. 240: 73-94.
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