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  • 1
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    Aqueously altered igneous rocks sampled on the floor of Jezero crater, Mars
    American Association for the Advancement of Science (AAAS) ; 2022
    In:  Science Vol. 377, No. 6614 ( 2022-09-30)
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 377, No. 6614 ( 2022-09-30)
    Abstract: The Perseverance rover landed in Jezero crater on Mars on 18 February 2021 with three scientific objectives: to explore the geologic setting of the crater, to identify ancient habitable environments and assess the possibility of past martian life, and to collect samples for potential transport to Earth for analysis in laboratories. In the 290 martian days (sols) after landing, Perseverance explored rocks of the Jezero crater floor. RATIONALE Jezero, a 45-km-diameter crater, was selected for investigation by Perseverance because orbital observations had shown that it previously contained an open-system lake, prior to ~3.5 billion years ago. Major climate change then left Mars in its current cold and dry state. On Earth, broadly similar environments of similar age to Jezero contain evidence of microbial life. Jezero crater contains a well-preserved delta, identified as a target for astrobiological investigation by the rover. Perseverance landed ~2 km away from the delta, on rocks of the crater floor. Previously proposed origins for these rocks have ranged from lake (or river) sediments to lava flows. Olivine-rich rocks identified on the crater floor, as well as in the area surrounding Jezero, have previously been attributed to a widely distributed impact melt or volcanic deposit, variably altered to carbonate. We used Perseverance to investigate the origin of the crater floor rocks and to acquire samples of them. RESULTS The Jezero crater floor consists of two geologic units: the informally named Máaz formation covers much of the crater floor and surrounds the other unit, which is informally named the Séítah formation. Máaz rocks display a range of morphologies: structureless boulders, flagstone-like outcrops, and ridges that are several meters high. The ridges expose prominent layers, ranging in thickness from a few centimeters to a few tens of centimeters. Rocks of Séítah are often tabular and strongly layered, with layer thicknesses ranging from centimeters to meters. Máaz and Séítah rocks display no outcrop or grain-scale evidence for transport by wind or water. Perseverance observations show that the Máaz rocks consist of 0.5- to 1-mm interlocking crystals of pyroxene and plagioclase. Combined with bulk chemical composition measurements, this suggests Máaz is an igneous unit that cooled slowly. In contrast, most Séítah rocks are very rich in magnesium and are dominated by densely packed 2- to 3-mm-diameter crystals of olivine, surrounded by pyroxene. These properties indicate settling and accumulation of olivine near the base of a thick magma body, such as an intrusion, lava lake, or thick lava flow. Ground-penetrating radar indicates that Séítah rocks dip beneath the Máaz formation. We hypothesize that Máaz could be the magmatic complement to the Séítah olivine-rich rocks or, alternatively, Máaz could be a series of basaltic lavas that flowed over and around the older Séítah formation. The olivines in the Séítah formation are rimmed with magnesium-iron carbonate, likely produced by interaction with CO 2 -rich water. Máaz formation rocks contain an aqueously deposited iron oxide or iron silicate alteration product. Both units commonly contain patches of bright-white salts, including sodium perchlorate and various sulfate minerals. Although both rock units have been altered by water, preservation of the original igneous minerals and the absence of aluminous clay minerals indicate that the alteration occurred under low water/rock ratio and that there was little loss of soluble species to the surroundings. It remains unclear when these aqueous processes occurred and whether they relate to the lake that once filled Jezero. The exposure of the olivine-rich Séítah rocks at the surface, the absence of lake or river sediment in the exploration area, and several nearby erosional remnant hills of delta sediment indicate that substantial crater floor erosion occurred after formation of these igneous units. Samples of both of these geologic units were collected as drill cores. The drill cores were stored in ultraclean sample tubes, for potential transport to Earth by future missions in the early 2030s. CONCLUSION The floor of Jezero crater explored by Perseverance consists of two distinct igneous units that have both experienced reactions with liquid water. Multiple rock cores were collected from these units for potential transport to Earth and analysis in terrestrial laboratories. Sample collection by Perseverance on Mars. This image mosaic was acquired by the WATSON camera on the rover’s robot arm. Rock cores were drilled from the two holes (arrow) in an igneous rock of the Máaz formation. The 6-cm-long, 1.3-cm-diameter cores were sealed into individual sample tubes and are now stored inside the rover.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.abo2196
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    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2022
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  • 2
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    The next frontier for planetary and human exploration
    Springer Science and Business Media LLC ; 2019
    In:  Nature Astronomy Vol. 3, No. 2 ( 2019-01-14), p. 116-120
    Details
    In: Nature Astronomy, Springer Science and Business Media LLC, Vol. 3, No. 2 ( 2019-01-14), p. 116-120
    Type of Medium: Online Resource
    ISSN: 2397-3366
    URL: Article
    DOI: 10.1038/s41550-018-0676-9
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2019
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  • 3
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    A new interpretation of total column BrO during Arctic spring : FRONTIER
    American Geophysical Union (AGU) ; 2010
    In:  Geophysical Research Letters Vol. 37, No. 21 ( 2010-11), p. n/a-n/a
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 37, No. 21 ( 2010-11), p. n/a-n/a
    Type of Medium: Online Resource
    ISSN: 0094-8276
    URL: Article
    DOI: 10.1029/2010GL043798
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2010
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  • 4
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    Past changes in the vertical distribution of ozone – Part 1: Measurement techniques, uncertainties and availability
    Copernicus GmbH ; 2014
    In:  Atmospheric Measurement Techniques Vol. 7, No. 5 ( 2014-05-21), p. 1395-1427
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 7, No. 5 ( 2014-05-21), p. 1395-1427
    Abstract: Abstract. Peak stratospheric chlorofluorocarbon (CFC) and other ozone depleting substance (ODS) concentrations were reached in the mid- to late 1990s. Detection and attribution of the expected recovery of the stratospheric ozone layer in an atmosphere with reduced ODSs as well as efforts to understand the evolution of stratospheric ozone in the presence of increasing greenhouse gases are key current research topics. These require a critical examination of the ozone changes with an accurate knowledge of the spatial (geographical and vertical) and temporal ozone response. For such an examination, it is vital that the quality of the measurements used be as high as possible and measurement uncertainties well quantified. In preparation for the 2014 United Nations Environment Programme (UNEP)/World Meteorological Organization (WMO) Scientific Assessment of Ozone Depletion, the SPARC/IO3C/IGACO-O3/NDACC (SI2N) Initiative was designed to study and document changes in the global ozone profile distribution. This requires assessing long-term ozone profile data sets in regards to measurement stability and uncertainty characteristics. The ultimate goal is to establish suitability for estimating long-term ozone trends to contribute to ozone recovery studies. Some of the data sets have been improved as part of this initiative with updated versions now available. This summary presents an overview of stratospheric ozone profile measurement data sets (ground and satellite based) available for ozone recovery studies. Here we document measurement techniques, spatial and temporal coverage, vertical resolution, native units and measurement uncertainties. In addition, the latest data versions are briefly described (including data version updates as well as detailing multiple retrievals when available for a given satellite instrument). Archive location information for each data set is also given.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-7-1395-2014
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2014
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  • 5
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    Past changes in the vertical distribution of ozone – Part 3: Analysis and interpretation of trends
    Copernicus GmbH ; 2015
    In:  Atmospheric Chemistry and Physics Vol. 15, No. 17 ( 2015-09-07), p. 9965-9982
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 15, No. 17 ( 2015-09-07), p. 9965-9982
    Abstract: Abstract. Trends in the vertical distribution of ozone are reported and compared for a number of new and recently revised data sets. The amount of ozone-depleting compounds in the stratosphere (as measured by equivalent effective stratospheric chlorine – EESC) was maximised in the second half of the 1990s. We examine the periods before and after the peak to see if any change in trend is discernible in the ozone record that might be attributable to a change in the EESC trend, though no attribution is attempted. Prior to 1998, trends in the upper stratosphere (~ 45 km, 4 hPa) are found to be −5 to −10 % per decade at mid-latitudes and closer to −5 % per decade in the tropics. No trends are found in the mid-stratosphere (28 km, 30 hPa). Negative trends are seen in the lower stratosphere at mid-latitudes in both hemispheres and in the deep tropics. However, it is hard to be categorical about the trends in the lower stratosphere for three reasons: (i) there are fewer measurements, (ii) the data quality is poorer, and (iii) the measurements in the 1990s are perturbed by aerosols from the Mt Pinatubo eruption in 1991. These findings are similar to those reported previously even though the measurements for the main satellite and ground-based records have been revised. There is no sign of a continued negative trend in the upper stratosphere since 1998: instead there is a hint of an average positive trend of ~ 2 % per decade in mid-latitudes and ~ 3 % per decade in the tropics. The significance of these upward trends is investigated using different assumptions of the independence of the trend estimates found from different data sets. The averaged upward trends are significant if the trends derived from various data sets are assumed to be independent (as in Pawson et al., 2014) but are generally not significant if the trends are not independent. This occurs because many of the underlying measurement records are used in more than one merged data set. At this point it is not possible to say which assumption is best. Including an estimate of the drift of the overall ozone observing system decreases the significance of the trends. The significance will become clearer as (i) more years are added to the observational record, (ii) further improvements are made to the historic ozone record (e.g. through algorithm development), and (iii) the data merging techniques are refined, particularly through a more rigorous treatment of uncertainties.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-15-9965-2015
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2015
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  • 6
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    A cohesive total ozone data set from the SBUV(/2) satellite system : SBUV/(2) TOTAL OZONE DATA
    American Geophysical Union (AGU) ; 2002
    In:  Journal of Geophysical Research: Atmospheres Vol. 107, No. D23 ( 2002-12-16), p. ACH 11-1-ACH 11-8
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 107, No. D23 ( 2002-12-16), p. ACH 11-1-ACH 11-8
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2001JD000853
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2002
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  • 7
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    Meteor 3/total ozone mapping spectrometer observations of the 1993 ozone hole
    American Geophysical Union (AGU) ; 1995
    In:  Journal of Geophysical Research: Atmospheres Vol. 100, No. D2 ( 1995-02-20), p. 2973-2983
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 100, No. D2 ( 1995-02-20), p. 2973-2983
    Abstract: The development of the springtime (September–November) Antarctic ozone hole was observed by the Meteor 3/total ozone mapping spectrometer (TOMS) to result in the lowest ozone value, 85 DU (Dobson units) on October 8, 1993, ever measured by TOMS. During late September and early October the region of extremely low ozone values was centered on the geographical pole between 85°S and 90°S. The geographical extent of the ozone hole region, the area within the 220‐DU contour, reached a maximum during the first week in October at a near‐circular area covering 24×10 6 km 2 reaching to the southern tip of South America. This approximately matched the 1992 area record. After the maximum area was reached in early October, the 1993 ozone hole region was significantly larger than during 1992 throughout the remainder of the month of October. The very low ozone values over the Antarctic continent have been confirmed by independent ground‐based data. Unlike 1992, the formation of the 1993 Antarctic ozone hole does not coincide with unusually low ozone values observed over most of the globe for the past 2 years. The most recent ozone data from Meteor 3/TOMS show that there has been a recovery at all latitudes from the extraordinarily low values observed during 1992 and part of 1993 after the June 1991 eruption of Mount Pinatubo. Meteor 3/TOMS is described and compared with Nimbus 7/TOMS during the 1991 to May 1993 overlap period. Observations of the 1992 ozone hole are presented from both instruments and are shown to agree within 5 DU.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/94JD02316
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1995
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  • 8
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    Trends in global tropospheric ozone inferred from a composite record of TOMS/OMI/MLS/OMPS satellite measurements and the MERRA-2 GMI simulation
    Copernicus GmbH ; 2019
    In:  Atmospheric Chemistry and Physics Vol. 19, No. 5 ( 2019-03-13), p. 3257-3269
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 19, No. 5 ( 2019-03-13), p. 3257-3269
    Abstract: Abstract. Past studies have suggested that ozone in the troposphere has increased globally throughout much of the 20th century due to increases in anthropogenic emissions and transport. We show, by combining satellite measurements with a chemical transport model, that during the last four decades tropospheric ozone does indeed indicate increases that are global in nature, yet still highly regional. Satellite ozone measurements from Nimbus-7 and Earth Probe Total Ozone Mapping Spectrometer (TOMS) are merged with ozone measurements from the Aura Ozone Monitoring Instrument/Microwave Limb Sounder (OMI/MLS) to determine trends in tropospheric ozone for 1979–2016. Both TOMS (1979–2005) and OMI/MLS (2005–2016) depict large increases in tropospheric ozone from the Near East to India and East Asia and further eastward over the Pacific Ocean. The 38-year merged satellite record shows total net change over this region of about +6 to +7 Dobson units (DU) (i.e., ∼15 %–20 % of average background ozone), with the largest increase (∼4 DU) occurring during the 2005–2016 Aura period. The Global Modeling Initiative (GMI) chemical transport model with time-varying emissions is used to aid in the interpretation of tropospheric ozone trends for 1980–2016. The GMI simulation for the combined record also depicts the greatest increases of +6 to +7 DU over India and East Asia, very similar to the satellite measurements. In regions of significant increases in tropospheric column ozone (TCO) the trends are a factor of 2–2.5 larger for the Aura record when compared to the earlier TOMS record; for India and East Asia the trends in TCO for both GMI and satellite measurements are ∼+3 DU decade−1 or greater during 2005–2016 compared to about +1.2 to +1.4 DU decade−1 for 1979–2005. The GMI simulation and satellite data also reveal a tropospheric ozone increases in ∼+4 to +5 DU for the 38-year record over central Africa and the tropical Atlantic Ocean. Both the GMI simulation and satellite-measured tropospheric ozone during the latter Aura time period show increases of ∼+3 DU decade−1 over the N Atlantic and NE Pacific.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    URL: Article
    DOI: 10.5194/acp-19-3257-2019
    DOI: 10.5194/acp-19-3257-2019-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
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  • 9
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    Record Low Global Ozone in 1992
    American Association for the Advancement of Science (AAAS) ; 1993
    In:  Science Vol. 260, No. 5107 ( 1993-04-23), p. 523-526
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 260, No. 5107 ( 1993-04-23), p. 523-526
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.260.5107.523
    RVK:
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    RVK:
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    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 1993
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  • 10
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    Recent biomass burning in the tropics and related changes in tropospheric ozone : BIOMASS BURNING AND TROPOSPHERIC OZONE
    American Geophysical Union (AGU) ; 2009
    In:  Geophysical Research Letters Vol. 36, No. 15 ( 2009-08-16), p. n/a-n/a
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 36, No. 15 ( 2009-08-16), p. n/a-n/a
    Type of Medium: Online Resource
    ISSN: 0094-8276
    URL: Article
    DOI: 10.1029/2009GL039303
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2009
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