Thomas Kneissl

Freie Universität Berlin | FUB · Institute of Geological Sciences

A 1:4M global geologic map of dwarf planet (1) Ceres was completed by the science team from NASAs Dawn mission, derived from images obtained during the Low Altitude Mapping Orbit (LAMO, 35 m/px). The map was published on the cover of Icarus, volume 316, December 2018 issue, along with a series of papers describing the geology within Ceres quadrangl...

A 1:4M global geologic map of dwarf planet (1) Ceres was completed by the science team from NASAs Dawn mission, derived from images obtained during the Low Altitude Mapping Orbit (LAMO, 35 m/px). The map was published on the cover of Icarus, volume 316, December 2018 issue, along with a series of papers describing the geology within Ceres quadrangl...

The 90.5-km Occator crater, with its peculiar and unique bright spots, is one of the most prominent and renowned feature on Ceres. Occator attracted broad public attention in scientific media as it is proposed to exhibit signs of post-impact cryovolcanic activity. In order to understand the time sequence of deposition, several attempts were made du...

The analysis of crater size‐frequency distributions (CSFDs) is a widely used technique to date and investigate planetary surface processes. There are two well‐established crater measurement techniques, traditional crater counting (TCC) and buffered crater counting (BCC), and two new geometric corrections, non‐sparseness correction (NSC) and buffere...

The lunar cratering record provides valuable information about the late accretion history of the inner Solar System. However, our understanding of the origin, rate, and timing of the impacting projectiles is far from complete. To learn more about these projectiles, we can examine crater size-frequency distributions (CSFDs) on the Moon. Here, we re-...

Dawn is the first spacecraft to visit and orbit Ceres, the largest object in the asteroid belt and the only dwarf planet in the inner Solar System. The Dawn science team undertook a systematic geologic mapping campaign of Ceres' entire surface. Here we present our contribution to this mapping campaign, a geologic map and geologic history of the Ezi...

The Dawn Framing Camera repeatedly imaged Ceres' North Pole quadrangle (Ac-1 Asari, latitudes >66°N) at a resolution of ∼35m/pixel through a panchromatic filter, enabling the derivation of a digital terrain model (DTM) and an ortho-rectified mosaic. Using this dataset, a photo-geologic map and stratigraphy, complemented with absolute model ages of...

We conducted a geologic mapping investigation of Dawn spacecraft data to determine the geologic history of the Kerwan impact basin region of dwarf planet Ceres, which is mostly located in the Ac-7 Kerwan Quadrangle. Geological mapping was applied to Dawn Framing Camera images from the Low Altitude Mapping Orbit (LAMO, 35[U+202F]m/pixel) and supplem...

The Dawn spacecraft arrived at dwarf planet Ceres in spring 2015 and imaged its surface from four successively lower polar orbits at ground sampling dimensions between ∼1.3[U+202F]km/px and ∼35[U+202F]m/px. To understand the geological history of Ceres a mapping campaign was initiated to produce a set of 15 quadrangle-based geological maps using th...

Prior to the arrival of the Dawn spacecraft at Ceres, the dwarf planet was anticipated to be ice-rich. Searches for morphological features related to ice have been ongoing during Dawn's mission at Ceres. Here we report the identification of pitted terrains associated with fresh Cerean impact craters. The Cerean pitted terrains exhibit strong morpho...

Since its arrival at Ceres, Dawn's Framing Camera has been imaging the dwarf planet at different altitudes, using 8 different filters. Based on these images, global clear filter mosaics, digital terrain models, and global color mosaics were produced. These datasets are basis for the derived photo-geologic map of the Ac-2 Coniraya quadrangle, locate...

The purpose of this paper is to introduce the Geologic Mapping of Ceres Special Issue of Icarus, which contains papers that include geological maps of the surface of dwarf planet Ceres derived from NASA's Dawn mission data. These maps were made to support analyses conducted by the Dawn Science Team during the Ceres Nominal Mission (March 2015–June...

Introduction: Ceres, the largest object in the main asteroid belt, has a low bulk density of 2,162 kgm-3 [1] suggesting large quantities of water (liquid and/or solid) being present within the outer layer and mantle as models predicted [2-4]. Portions of water-ice prevalent in the upper surface sublimates and a fraction of this water can potentiall...

This study presents the mapping strategy and geological history of the Rongo quadrangle of Ceres.

Ceres, a dwarf planet located in the main asteroid belt, has a low bulk density 1 , and models predict that a substantial amount of water ice is present in its mantle and outer shell 2–4 . The Herschel telescope and the Dawn spacecraft 5 have observed the release of water vapour from Ceres 6,7 , and exposed water ice has been detected by Dawn on it...

On Ceres, multispectral imaging data from the Dawn spacecraft shows a distinct bluish characteristic for recently exposed material from the subsurface in, for example, crater ejecta. Ejecta blankets of presumably old craters show a more reddish spectrum. We selected areas in which fresh material from the Cerean subsurface was exposed at a specific...

Since March 6 2015 the Dawn spacecraft (Russell et al., 2012) is orbiting the dwarf planet Ceres inside the asteroid main belt. Color ratio data of the Framing Camera instrument show distinct bluish characteristics of recently exposed materials such as impact ejecta of young craters. Besides the common radial pattern of proximal ejecta, the distrib...

In the last decades, the exploration of planets and moons by spacecraft revealed a variety of volcanic expressions. The recent visit to dwarf planet Ceres by the Dawn spacecraft is shedding light on a possible new, compositionally different volcanism falling into the cryovolcanism field. The dwarf planet’s properties, i.e., low bulk density, low in...

INTRODUCTION Classic volcanism prevalent on terrestrial planets and volatile-poor protoplanets, such as asteroid Vesta, is based on silicate chemistry and is often expressed by volcanic edifices (unless erased by impact bombardment). In ice-rich bodies with sufficiently warm interiors, cryovolcanism involving liquid brines can occur. Smooth plains...

INTRODUCTION Thermochemical models have predicted that the dwarf planet Ceres has, to some extent, formed a mantle. Moreover, due to viscous relaxation, these models indicate that Ceres should have an icy crust with few or no impact craters. However, the Dawn spacecraft has shown that Ceres has elevation excursions of ~15 km, cliffs, graben, steep-...

Before NASA's Dawn mission, the dwarf planet Ceres was widely believed to contain a substantial ice-rich layer below its rocky surface. The existence of such a layer has significant implications for Ceres's formation, evolution, and astrobiological potential. Ceres is warmer than icy worlds in the outer Solar System and, if its shallow subsurface i...

We here propose a new technique to derive crater size-frequency distributions (CSFDs) from non-sparsely cratered surfaces, by accounting for the loss of craters due to subsequent crater/ejecta coverage. This approach, which we refer to as the buffered non-sparseness correction (BNSC), relates each crater to a measurement area found by excluding reg...

The predictions of crater chronology models have customarily been evaluated by dividing a crater population into discrete diameter intervals, plotting the crater density for each, and finding a best-fit model isochron, with the uncertainty in the procedure being assessed using 1/√n estimates, where n is the number of craters in an interval. This ap...

The Framing Camera (FC) onboard the Dawn spacecraft acquired several spectral data sets of (1) Ceres with increasing spatial resolution (up to 135 m/pixel with nearly global coverage). The FC is equipped with seven color filters (0.4–1.0 µm) plus one panchromatic ('clear') filter [1]. We produced spectral mosaics using photometrically corrected FC...

Global, regional and local mosaics of the Dawn FC2 framing camera are used for geologic mapping and stratigraphic investigation of the surface of dwarf planet (1) Ceres

Geologic mapping and measurements of the crater size-frequency distribution are carried out in order to derive a time-stratigraphy of dwarf planet (1) Ceres

The dwarf planet (1) Ceres, the largest object in the main asteroid belt with a mean diameter of about 950 kilometres, is located at a mean distance from the Sun of about 2.8 astronomical units (one astronomical unit is the Earth-Sun distance). Thermal evolution models suggest that it is a differentiated body with potential geological activity. Unl...

After more than ten years in orbit at Mars, the coverage from the High Resolution Stereo Camera (HRSC) on the European Space Agency’s Mars Express is sufficient to begin constructing mosaic products on a global scale. We describe our systematic processing procedure and, in particular, the technique used to bring images affected by atmospheric dust...

We present a photo-geological map of the “Asari” quadrangle covering the North Pole area of Ceres (66°N-90°N), based on Dawn Framing Camera images and mosaics with a resolution of ~400 m/pixel. The mapping process is supported by a stereo- photogrammetric digital elevation model. We identified few isolated plateaus of up to ~5 km in altitude relati...

On March 6, 2015, the Dawn spacecraft was captured into orbit around Ceres. During its appraoch phase since Dec. 1, 2014, imaging data returned by the framing camera (FC) have increased in spatial resolution exceeding that of the Hubble Space Telescope. In this paper, we use the first images to identify and map global geologic units and to establis...

We present a preliminary crater production and chronology function for Ceres for initial estimates of surface ages from early Dawn imaging data of Ceres.

Introduction: Mars Express HRSC image strips show varying brightnesses caused by differing illumination and atmospheric conditions. Lambert correction improves the situation [1], but not sufficiently for a visually consistent mosaic (Fig 1).

We present crater data from Mimas and compare the measured crater size-frequency distribution with previously published crater production functions derived from the cometary size-distribution and a lunar-like version

We have performed extensive analyses of size-frequency distributions accumulated on ejecta blankets of 42 fresh primary craters on Vesta.

We have measured size-frequency distributions of sub-km impact craters on fresh units on Vesta and performed weighted least squares regression analyses. Derived power-law exponents were then compared with the two currently used production functions.

The High Resolution Stereo Camera (HRSC) is a push-broom image sensor onboard Mars Express recording the Martian surface in 3D and color. Being in orbit since 2004, the camera has obtained over 3,600 panchromatic image sequences covering about 70% of the planet's surface at 10-20 m/pixel. The composition of an homogenous global mosaic is a major ch...

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NASA’s Dawn spacecraft entered orbit of Ceres on March 6, 2015, to spend one year characterizing the geology, elemental and mineralogical composition, topography, shape, and internal structure of the Ceres [1]. Ceres is supposed to be differentiated into a silicate core, a liquid water mantle and a solid ice crust with a surface temperature from 13...

We produced a geologic map of the Av-9 Numisia quadrangle of asteroid Vesta using Dawn spacecraft data to serve as a tool to understand the geologic relations of surface features in this region. These features include the plateau Vestalia Terra, a hill named Brumalia Tholus, and an unusual “dark ribbon” material crossing the majority of the map are...

We used Dawn spacecraft data to identify and delineate geological units and landforms in the Marcia quadrangle of Vesta as a means to assess the role of the large, relatively young impact craters Marcia (~63. km diam.) and Calpurnia (~53. km diam.) and their surrounding ejecta field on the local geology. We also investigated a local topographic hig...