The making of Martian meteorite Block Island

Beech, Martin; Coulson, Ian M.

doi:10.1111/j.1365-2966.2010.16350.x

Cited by 3 publications

(4 citation statements)

References 29 publications

(34 reference statements)

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“…Kieffer and Zent (1992) estimate the amount of CO 2 absorbed in the regolith could be as much as 70 mbar equivalent. The discovery of sizable iron meteorites by the Opportunity rover has been cited as evidence for a past thicker atmosphere (Beech and Coulson 2010;Chappelow and Sharpton 2006) though Chappelow and Golombek (2010) have found these meteorites could have been decelerated enough in the present-day atmosphere to survive impact under a narrow range of initial entry conditions.…”

Section: Atmospheric Filteringmentioning

confidence: 99%

Dating very young planetary surfaces from crater statistics: A review of issues and challenges

Williams

Bogert

Pathare

et al. 2017

Meteorit & Planetary Scien

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Abstract-Determining the ages of young planetary surfaces relies on using populations of small, often sub-km diameter impact craters due to the higher frequency at which they form. Smaller craters however can be less reliable for estimating ages as their sizefrequency distribution is more susceptible to alteration with debate as to whether they should be used at all. With the current plethora of meter-scale resolution images acquired of the lunar and Martian surfaces, small craters have been widely used to derive model ages to establish the temporal relation of recent geologic events. In this review paper, we discuss the many factors that make smaller craters particularly challenging to use and should be taken into consideration when crater counts are confined to small crater diameters. Establishing confidence in a model age ultimately requires an understanding of the geologic context of the surface being dated as reliability can vary considerably and limitations of the dating technique should be considered in applying ages to any geologic interpretation.

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Section: Atmospheric Filteringmentioning

confidence: 99%

Dating very young planetary surfaces from crater statistics: A review of issues and challenges

Williams

Bogert

Pathare

et al. 2017

Meteorit & Planetary Scien

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“…The length of time that these meteorites have been on or near the surface is difficult to estimate. The size and mass of Heat Shield Rock and Block Island have been used as evidence that they landed during a period when the atmosphere was denser and slowed their descent [ Beech and Coulson , 2010]. Otherwise they would have been destroyed during the subsequent hypervelocity impact with the surface.…”

Section: Cobble and Boulder‐sized Rock Fragmentsmentioning

confidence: 99%

Opportunity Mars Rover mission: Overview and selected results from Purgatory ripple to traverses to Endeavour crater

Arvidson¹,

et al. 2011

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[1] Opportunity has been traversing the Meridiani plains since 25 January 2004 (sol 1), acquiring numerous observations of the atmosphere, soils, and rocks. This paper provides an overview of key discoveries between sols 511 and 2300, complementing earlier papers covering results from the initial phases of the mission. Key new results include (1) atmospheric argon measurements that demonstrate the importance of atmospheric transport to and from the winter carbon dioxide polar ice caps; (2) observations showing that aeolian ripples covering the plains were generated by easterly winds during an epoch with enhanced Hadley cell circulation; (3) the discovery and characterization of cobbles and boulders that include iron and stony-iron meteorites and Martian impact ejecta; (4) measurements of wall rock strata within Erebus and Victoria craters that provide compelling evidence of formation by aeolian sand deposition, with local reworking within ephemeral lakes; (5) determination that the stratigraphy exposed in the walls of Victoria and Endurance craters show an enrichment of chlorine and depletion of magnesium and sulfur with increasing depth. This result implies that regional-scale aqueous alteration took place before formation of these craters. Most recently, Opportunity has been traversing toward the ancient Endeavour crater. Orbital data show that clay minerals are exposed on its rim. Hydrated sulfate minerals are exposed in plains rocks adjacent to the rim, unlike the surfaces of plains outcrops observed thus far by Opportunity. With continued mechanical health, Opportunity will reach terrains on and around Endeavour's rim that will be markedly different from anything examined to date.

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“…Recently, Beech and Coulson [2010] used methods similar to those used here for essentially the same purpose. They concluded that BI could not have landed under present Mars atmospheric conditions but would have required an atmosphere 10–100 times denser.…”

Section: Resultsmentioning

confidence: 99%

“…Two of these are even larger than HSR, and therefore reopen the question of whether Mars must have had a denser atmosphere in the past in order to explain them. Beech and Coulson [2010] concluded that massive iron meteorites (>800 kg) would require an atmosphere at least one to two orders of magnitude denser than at present. Finally, the discovery of several such large iron meteorites with similar composition, which should be very rare compared to other meteorites on Mars, in such close proximity raises the possibility that they represent a strewn field produced by a single event.…”

Section: Introductionmentioning

confidence: 99%

Event and conditions that produced the iron meteorite Block Island on Mars

Chappelow¹,

Golombek²

2010

J. Geophys. Res.

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[1] The Mars Exploration Rover Opportunity has discovered four large iron-nickel meteorites that range in size from 50 to 240 kg dispersed over 10 km of Meridiani Planum, Mars. Because these meteorites are covered with hollows that resemble regmaglypts, their surfaces record their ablation through the atmosphere, and they must have landed at speeds below hypervelocity (<2 km s −1 ) to survive. Slowing massive iron meteorites requires a minimum atmospheric density, which was quantified using a numerical model that integrates the equations of motion for incoming meteoroids through an atmosphere of a given surface density and scale height and records their outcomes as direct (generally hypervelocity impacts that form craters), longer over the horizon and fallback flight paths, and skip outs. The present atmosphere of Mars is sufficient to slow iron meteoroids as large as Block Island (the most massive meteorite) via drag and significant ablation on long flight paths, although for standard distributions of entering meteoroid masses, velocities, and entry angles, such events are rare (0.007% of incoming iron meteoroids). Such events require entry angles of 10°-13°, entry velocities of 6-18 km s −1 , and entry masses of 225-710 kg. The absence of large stony meteorites is probably at least partially because they are much weaker and thus broken up into smaller fragments on impact. Although differential drag deceleration on long flight paths could disperse fragments of an entering meteoroid by tens of kilometers, dynamic pressures are too low to break up an iron meteorite, leaving the possibility that they are paired an open question.

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The making of Martian meteorite Block Island

Cited by 3 publications

References 29 publications

Dating very young planetary surfaces from crater statistics: A review of issues and challenges

Dating very young planetary surfaces from crater statistics: A review of issues and challenges

Opportunity Mars Rover mission: Overview and selected results from Purgatory ripple to traverses to Endeavour crater

Event and conditions that produced the iron meteorite Block Island on Mars

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