Papers by Patricio Becerra
Planetary and Space Science
A key outstanding question in Martian science is 'are the polar caps gaining or losing mass a... more A key outstanding question in Martian science is 'are the polar caps gaining or losing mass and what are the implications for past, current and future climate?' To address this question, we use observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) of the north polar cap during late summer for multiple Martian years, to monitor the summertime water cycle in order to place quantitative limits on the amount of water ice deposited and sublimed in late summer. We establish here for the first time the summer cycle of water ice absorption band signatures on the north polar cap. We show that in a key region in the interior of the north polar cap, the absorption band depths grow until Ls=120, when they begin to shrink, until they are obscured at the end of summer by the north polar hood. This behavior is transferable over the entire north polar cap, where in late summer regions 'flip' from being net sublimating into net condensation mode. This tra...
Image photometry reveals that the F ring is approximately twice as bright during the Cassini tour... more Image photometry reveals that the F ring is approximately twice as bright during the Cassini tour as it was during the Voyager flybys of 1980 and 1981. It is also three times as wide and has a higher integrated optical depth. We have performed photometric measurements of more than 4,800 images of Saturn's F ring taken over a five-year period with Cassini's Narrow Angle Camera. We show that the ring is not optically thin in many observing geometries and apply a photometric model based on single-scattering in the presence of shadowing and obscuration, deriving a mean effective optical depth tau = 0.033. Stellar occultation data from Voyager PPS and Cassini VIMS validate both the optical depth and the width measurements. In contrast to this decades-scale change, the baseline properties of the F ring have not changed significantly from 2004 to 2009. However, we have investigated one major, bright feature that appeared in the ring in late 2006. This transient feature increased th...
2018 5th IEEE International Workshop on Metrology for AeroSpace (MetroAeroSpace)
In the next decades, the planetary science community is preparing for the exploration of the Jupi... more In the next decades, the planetary science community is preparing for the exploration of the Jupiter system with NASA's Europa Clipper mission and ESA's JUICE mission. The main objective of these missions is to characterise the subsurface structure of the Jupiter's icy moons Ganymede, Europa and Callisto. These bodies may harbor shallow saline liquid water reservoirs, and ice/ocean interfaces at depth. Part of the scientific payload of these missions includes the REASON radar sounder on Clipper (which will operate at 9 MHz and 60 MHz) and the RIME radar sounder on JUICE (9 MHz). The effect of dissolved hydrated sulfate salts on the dielectric properties of pure water is not yet well understood, although it is crucial for the interpretation of the RIME and REASON data, in particular for the search and the characterisation of subsurface saline liquid water reservoirs and deep ice/ocean interfaces. In order to provide constrains from laboratory experiments, we set up a programme of dielectric spectroscopy measurements on pure and saline liquid water in the frequency range of 40 MHz to 1 GHz using a coaxial cell adapted for the measurements of liquids. In this paper, we report the first results of these experiments. Namely, ambient temperature measurements of one deionised liquid water sample, five samples consisting of sodium chloride salt dissolved in deionised liquid water, and three samples consisting of magnesium sulfate salt dissolved in purified liquid water. We show that, in the frequency range of the measurements, the effect on the complex permittivity of the dissolved magnesium sulfate salt is smaller than that of the dissolved sodium chloride. Besides, our results suggest to take into account a decrease of the real and the imaginary parts of the complex permittivity from 9 MHz to 60 MHz in radar propagation models involving a dielectric interface with a liquid water reservoir in which hydrated magnesium sulfate salts are dissolved.
Journal of Geophysical Research: Planets
One of the longest-standing questions related to these deposits was recently re-affirmed at the 5... more One of the longest-standing questions related to these deposits was recently re-affirmed at the 5 International Mars Polar Science and Exploration Conference: “What chronology, compositional variability, and record of climatic change is expressed in the stratigraphy of the PLD?” [2]. In order to attempt to answer this question, our first step is to accurately describe this stratigraphic record. This important step has been limited in the past due to the lack of layer-scale topographic data, which forced the use of quantities such as brightness to describe a layer. The Shallow Radar instrument (SHARAD) has detected reflectors within the NPLD that are interpreted to be depositional layers [3], and could be correlated to the visible strata [4]. This implies that, at least in the NPLD, the layers are laterally continuous, and form a coherent record of depositional conditions. Past researchers have attempted to extract periodic signals from stratigraphic sequences constructed from the br...
Institutional support York University, Planetary Science Institute, Centro Austral de Investigaci... more Institutional support York University, Planetary Science Institute, Centro Austral de Investigaciones Cientificas (CADIC-CONICET), University of Bern, International Association of Cryospheric Sciences, International Association of Geomorphologists, Lunar and Planetary Institute, Universities Space Research Association.
The Planetary Science Journal, 2021
Mars Polar Science is a subfield of Mars science that encompasses all studies of the cryosphere o... more Mars Polar Science is a subfield of Mars science that encompasses all studies of the cryosphere of Mars and its interaction with the Martian environment. Every 4 yr, the community of scientists dedicated to this subfield meets to discuss new findings and debate open issues in the International Conference on Mars Polar Science and Exploration (ICMPSE). This paper summarizes the proceedings of the seventh ICMPSE and the progress made since the sixth edition. We highlight the most important advances and present the most salient open questions in the field today, as discussed and agreed upon by the participants of the conference. We also feature agreed-upon suggestions for future methods, measurements, instruments, and missions that would be essential to answering the main open questions presented. This work is thus an overview of the current status of Mars Polar Science and is intended to serve as a road map for the direction of the field during the next 4 yr and beyond, helping to sha...
Experimental Astronomy, 2021
Current plans within the European Space Agency (ESA) for the future investigation of Mars (after ... more Current plans within the European Space Agency (ESA) for the future investigation of Mars (after the ExoMars programme) are centred around participation in the Mars Sample Return (MSR) programme led by NASA. This programme is housed within the Human and Robotic Exploration (HRE) Directorate of ESA. This White Paper, in response to the Voyage 2050 call, focuses on the important scientific objectives for the investigation of Mars outside the present HRE planning. The achievement of these objectives by Science Directorate missions is entirely consistent with ESA’s Science Programme. We illustrate this with a theme centred around the study of the Martian polar caps and the investigation of recent (Amazonian) climate change produced by known oscillations in Mars’ orbital parameters. Deciphering the record of climate contained within the polar caps would allow us to learn about the climatic evolution of another planet over the past few to hundreds of millions of years, and also addresses ...
Introduction: The South Polar Layered Deposits (SPLD) of Mars are kms-thick stratified deposits o... more Introduction: The South Polar Layered Deposits (SPLD) of Mars are kms-thick stratified deposits of ice and dust, whose internal structure can be observed remotely through troughs that dissect their volume. Oscillations in Mars' astronomical parameters, which directly affect insolation and thus climate, are believed to be responsible for the layered accumulation of the PLD [1]. One of the main objectives of Mars polar science is to attempt to connect patterns in the bed structure to patterns in these oscillations, in order to "read" the Martian climate record [2]. Many observations and models of the North PLD support this theory of orbital forcing [2-7]. However, the SPLD (Fig. 1) appear to be orders of magnitude older than the NPLD [8,9], and the southern strata are thicker, darker, and more eroded than in the north [10-12]. In addition, Mars' orbital solutions become chaotic before 20 Ma [13], near the SPLD surface age, hindering the prospect for age dating the SPLD. Here, we measure periodicities in SPLD bedding exposures and compare them to the characteristic frequencies of Mars' insolation to test for astronomical forcing. We use Digital Terrain Models (DTMs) of SPLD outcrops made from stereo images taken by the HiRISE [14], along with the first DTM of the SPLD produced by TGO's CaSSIS [15]. We investigate discrepancies in the signals that may discriminate between different epochs of accumulation, and estimate accumulation rates. In addition, we compare the detected signals and stratigraphic profiles of the SPLD to those of the NPLD, to investigate the relationship between orbitally forced accumulation in Mars' polar caps. Data and Methods: Our dataset (Fig. 1a) is 15 HiRISE DTMs (e.g. Fig. 1b,c, [16]) and 1 CaSSIS DTM (Fig. 1d) of exposed SPLD beds. The CaSSIS stereo image pair was taken within the same orbit of TGO [15], and the DTM was produced using the 3DPD pipeline [17]. The stratigraphic analysis was performed on linear profiles of depth-varying bed properties, or "virtual ice cores" of the SPLD. We extracted profiles of bed protrusion within a 350m window, a proxy for resistance to erosion [18]. For both, five profiles ~10 m apart along-strike are averaged to minimize noise. An example profile is shown in Fig. 2a. We searched for periodicities in the profiles using wavelet analysis [19]. The depth-varying wavelet power spectrum (WPS, Fig. 2a) reveals dominant forcing wavelengths in the profile, and their depth-dependence. To ensure statistical significance, we required the detected wavelengths have higher power than 95% of 10000 red noise background simulations (Fig. 2a;
We present a preliminary correlation of visible imagery and stereo-topography from HiRISE with su... more We present a preliminary correlation of visible imagery and stereo-topography from HiRISE with sub-surface radar from SHARAD of Mars’ NPLD.
The CaSSIS (Colour and Stereo Surface Imaging System) [1] of the ExoMars Trace Gas Orbiter (TGO) ... more The CaSSIS (Colour and Stereo Surface Imaging System) [1] of the ExoMars Trace Gas Orbiter (TGO) has already acquired numerous images of Mars that show seasonal and diurnal ices and frosts at the surface as well as clouds and fog in the atmosphere. Simulations of the CaSSIS signal in all four colour filters from laboratory measurements with analogues and data from other missions will be helpful to interpret these new observations
Introduction: A long-standing goal of polar science on Mars has been understanding the paleoclima... more Introduction: A long-standing goal of polar science on Mars has been understanding the paleoclimate record of ice deposits. A special focus is placed on confirming or refuting the hypothesis that planetary climate is strongly driven by changes in orbital and axial parameters, like obliquity variations. Usually, research is focused on the north and south polar layered deposits (NPLD and SPLD), kms-thick sheets of nearly pure H2O ice. While great progress has been made in understanding the records within these deposits [e.g., 1–5], decades of research has ultimately not yet fully deciphered and age-dated an orbital signal, which may be difficult to identify even if it is present [6, 7]. One way to address this issue is to consider other, smaller ice deposits that are not connected to the PLDs. Outlier ice deposits exist as mounds within impact craters in both polar regions of Mars. Because they are at lower latitudes than the PLDs, they may be more sensitive to climate change [8] and ...
Both Mars and Triton have a so-called “Vapor Pressure” atmosphere, in which the main constituent ... more Both Mars and Triton have a so-called “Vapor Pressure” atmosphere, in which the main constituent of the atmosphere exists both as a vapor in the atmosphere and a condensate (i.e. “ice”) on the surface [1]. Our models for the features mentioned above track the distribution of surface ice (CO2 on Mars and N2 on Triton) throughout the year, by calculating the sublimation/condensation rate of frost in an energy balance equation [2]:
Introduction: The CO2 ice South Polar Residual Cap (SPRC) may be a sensitive indicator of the int... more Introduction: The CO2 ice South Polar Residual Cap (SPRC) may be a sensitive indicator of the interannual variability of the martian climate. Imaging of the martian south polar region by HiRISE [1], and CTX [2] found that many of the scarps and pits that compose the so-called “Swiss cheese terrain” [3] of the SPRC exhibited a bright “halo” (fig.1) around their edges during midsummer of Mars Year (MY) 28 [4]. The MY28 southern summer included a global dust storm at ~Ls 260 that could have altered the thermal environment of the SPRC such that these halos formed from sublimation differences in the terrain. Our goal is to understand the climatic difference at the south pole between MY28 and other years through the detailed study of the surface changes that took place, namely CO2 frost falos on the edges of swiss cheese features.
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Papers by Patricio Becerra