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Author

Jouko Raitala

Bio: Jouko Raitala is an academic researcher from University of Oulu. The author has contributed to research in topics: Impact crater & Mars Exploration Program. The author has an hindex of 16, co-authored 85 publications receiving 806 citations.


Papers
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Journal ArticleDOI
TL;DR: The Circum-Hellas Volcanic Province (CHVP) as discussed by the authors contains the six oldest central vent volcanoes on Mars, which formed after the Hellas impact basin, between 4.0 and 3.6

91 citations

Journal ArticleDOI
TL;DR: In this article, the authors used Mars Express High Resolution Stereo Camera images of the Tyrrhena Patera volcano to assign cratering model ages to material units defined in the VikingOrbiter-based geologic mapping.
Abstract: [1] We used Mars Express High Resolution Stereo Camera images of the Tyrrhena Patera volcano to assign cratering model ages to material units defined in the VikingOrbiter-based geologic mapping. Cratering model ages are generally consistent with their stratigraphy. We can identify three key intervals of major activity at Tyrrhena Patera: (1) formation of the volcanic edifice in the Noachian Period, ∼3.7–4.0 Ga, shortly following the Hellas impact (∼4 Ga) and coincident with the formation of Hadriaca Patera (∼3.9 Ga); (2) modification of the edifice and formation of the caldera rille and channels in the Hesperian Period, possibly extending into the Amazonian Period; and (3) a final stage of modification in the Late Amazonian Epoch, ∼0.8–1.4 Ga. Early- to mid-Hesperian activity on Tyrrhena Patera is consistent with similar activity on Hadriaca Patera at ∼3.3–3.7 Ga. The most recent dateable event on Tyrrhena Patera is modification on the upper shield, caldera rille, and channel floors at ∼800 Ma. This coincidence of resurfacing in three units suggests a widespread process(es), which we speculate involved preferential (aeolian?) erosion of small craters on these flatter surfaces relative to the other units on the volcano. Alternatively, some combination of pyroclastic flow emplacement on the upper shield and fluvial activity in the caldera rille and channels, followed by differential aeolian erosion and deposition, could have produced the present surface. Regardless, major geologic resurfacing ended at Tyrrhena Patera nearly a billion years ago.

47 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used high-resolution stereo camera images of Hadriaca Patera, Mars, to reveal morphologic details about this volcano and enable determination of a chronology of the major geologic events through new cratering age assessments.
Abstract: [1] High Resolution Stereo Camera (HRSC) images of Hadriaca Patera, Mars, in combination with Mars Orbiter Camera (MOC), Mars Orbiter Laser Altimeter (MOLA), and Thermal Infrared Imaging System (THEMIS) data sets, reveal morphologic details about this volcano and enable determination of a chronology of the major geologic events through new cratering age assessments. New topographic measurements of the Hadriaca edifice were also made from a HRSC-based high-resolution (125 m) digital terrain model (DTM) and compared to the MOLA DTM. We find evidence for a complex formation and erosional history at Hadriaca Patera, in which volcanic, fluvial, and aeolian processes were all involved. Crater counts and associated model ages suggest that Hadriaca Patera formed from early shield-building volcanic (likely explosive pyroclastic) eruptions at ∼3.7–3.9 Ga, with caldera formation no later than ∼3.5 Ga. A variety of geologic activity occurred in the caldera and on the northern flank and plains at ∼3.3–3.5 Ga, likely including pyroclastic flows (that partially filled a large crater NW of the caldera, and plains to the NE) and differential erosion/deposition by aeolian and/or fluvial activity. There were some resurfacing event(s) in the caldera and on the eastern flank at ∼2.4–2.6 Ga, in which the eastern flank's morphology is indicative of fluvial erosion. The most recent dateable geologic activity on Hadriaca Patera includes caldera resurfacing by some process (most likely differential aeolian erosion/deposition) in the Amazonian Period, as recent as ∼1.5 Ga. This is coincident with the resurfacing of the heavily channeled south flank by fluvial erosion. Unlike the Tharsis shields, major geologic activity ended at Hadriaca Patera over a billion years ago.

46 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a new approach to Venus landing site selection that would avoid the potential contamination by ejecta from upwind impact craters by combining the desire to study materials of specific geologic units with the problem of avoiding potential contamination from up-warping impacts.

46 citations

Journal ArticleDOI
TL;DR: In this paper, the High Resolution Stereo Color camera (HRSC) data over Hesperia Planum and its surroundings reveal important details of geologic episodes and water-related processes in this region.
Abstract: [1] The High Resolution Stereo Color camera (HRSC) data over Hesperia Planum and its surroundings reveal important details of geologic episodes and water-related processes in this region. (1) The Noachian fluvial events of Hesperia Planum depression included accumulation of water and formation of a water/ice reservoir there. Later, the reservoir was depleted in several phases reflecting diminishing amounts of water. Climate changes and/or volcanism were important in these volatile releases. (2) The massive, 0.45–1.5 × 106 km3, erosion from the Hesperia depression before the main lava eruption possibly resulted in thick, 0.5–1.5 km, deposits in Hellas Planitia. (3) Measurements of the flooded craters within Hesperia Planum provide the estimates of the thickness of lavas there, about 250–500 m. The final volume of lavas within Hesperia Planum (0.4–0.7 × 106 km3) is comparable with the range of some terrestrial igneous provinces such as Columbia River Basalts. (4) Extended magmatism possibly triggered formation of the outflow channel in a few locations after the lava emplacement. During this episode, about 0.04 × 106 km3 of material (about 4.5–8.9% of the volume eroded in the episode of massive erosion) were removed. The thickness of the composite lava layer exposed on the walls of the outflow channels, a few hundreds of meters, corresponds well to the thickness estimates made by the measurements of the flooded craters. (5) Dispersed viscous flows (debris aprons, flow-like deposits) reflect the final fluvial events. Viscous flows from the subsurface sources in the Southwestern trough associate with Dao, Niger, and Harmakhis Valles. These flows represent the final volatile discharge from the Hesperia reservoir that mostly was depleted by the earlier events of massive erosion and formation of the outflow channels. Viscous surface flows are mostly associated with Reull Vallis and probably reflect redistribution of volatiles related to the late episodes of evolution of this outflow channel.

38 citations


Cited by
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10 Jul 1986
TL;DR: In this paper, a multispectral image was modeled as mixtures of reflectance spectra of palagonite dust, gray andesitelike rock, and a coarse rock-like soil.
Abstract: A Viking Lander 1 image was modeled as mixtures of reflectance spectra of palagonite dust, gray andesitelike rock, and a coarse rocklike soil. The rocks are covered to varying degrees by dust but otherwise appear unweathered. Rocklike soil occurs as lag deposits in deflation zones around stones and on top of a drift and as a layer in a trench dug by the lander. This soil probably is derived from the rocks by wind abrasion and/or spallation. Dust is the major component of the soil and covers most of the surface. The dust is unrelated spectrally to the rock but is equivalent to the global-scale dust observed telescopically. A new method was developed to model a multispectral image as mixtures of end-member spectra and to compare image spectra directly with laboratory reference spectra. The method for the first time uses shade and secondary illumination effects as spectral end-members; thus the effects of topography and illumination on all scales can be isolated or removed. The image was calibrated absolutely from the laboratory spectra, in close agreement with direct calibrations. The method has broad applications to interpreting multispectral images, including satellite images.

1,107 citations

01 Jan 1996
TL;DR: In this paper, the amount of water outgassed from Mars by impact erosion and hydrodynamic escape is estimated to be between 6 to 160 m. The two sets of estimates may be reconciled if early in its history, Mars lost part of its atmosphere.
Abstract: Estimates of the amount of water outgassed from Mars, based on the composition of the atmosphere, range from 6 to 160 m, as compared with 3 km for the Earth. In contrast, large flood features, valley networks, and several indicators of ground ice suggest that at least 500 m of water have outgassed. The two sets of estimates may be reconciled if early in its history, Mars lost part of its atmosphere by impact erosion and hydrodynamic escape.

910 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe the procedure to fit a cumulative production function polynomial to a partial crater size-frequency distribution, and demonstrate its use in obtaining times for both the surface formation and the resurfacing event.

534 citations

Journal ArticleDOI
01 Nov 2008-Icarus
TL;DR: A catalog of 210 open-basin lakes (lakes with outlet valleys) fed by valley networks showed that they are widely distributed in the Noachian uplands of Mars as mentioned in this paper.

414 citations

Journal ArticleDOI
TL;DR: In this article, a cost-effective methodology involving satellite remote sensing images and statistics has been discussed, where multidimensional satellite images have been used to demarcate shoreline positions, from which shoreline change rates have been estimated using linear regression.

296 citations