ESA’s Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian syst... more ESA’s Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian system in the 2030s, combining a suite of state-of-the-art instruments with an orbital tour tailored to maximise observing opportunities. We review the Jupiter science enabled by the JUICE mission, building on the legacy of discoveries from the Galileo, Cassini, and Juno missions, alongside ground- and space-based observatories. We focus on remote sensing of the climate, meteorology, and chemistry of the atmosphere and auroras from the cloud-forming weather layer, through the upper troposphere, into the stratosphere and ionosphere. The Jupiter orbital tour provides a wealth of opportunities for atmospheric and auroral science: global perspectives with its near-equatorial and inclined phases, sampling all phase angles from dayside to nightside, and investigating phenomena evolving on timescales from minutes to months. The remote sensing payload spans far-UV spectroscopy (50-210 nm), visible i...
The seasonal deposition and sublimation of CO constitute a major element in the Martian volatile ... more The seasonal deposition and sublimation of CO constitute a major element in the Martian volatile cycle. Here, we propose to use the shadow variations of the ice blocks at the foot of the steep scarps of the North Polar Layered Deposits (NPLDs) to infer the vertical evolution of the seasonal deposits at high polar latitudes. We conduct an experiment at a steep scarp centered at (85.0°N, 151.5°E). We show that the average thickness of the seasonal deposits due to snowfalls in Mars Year 31 is 0.97±0.13 m at Ls = 350.7° in late winter, which then gradually decreases in springtime. The large snow depth measured makes us wonder if snowfalls are more frequent and violent than previously thought. Meanwhile, we show that the average frost thickness due to direct condensation in Mars Year 31 reaches 0.64±0.18 m at Ls = 350.7° in late winter and quasi-linearly decreases towards the summer solstice. Combined, the total thickness of the seasonal cover in Mars Year 31 reaches 1.63±0.22 m at Ls = ...
The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) onboard the European Spac... more The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) onboard the European Space Agency's Rosetta spacecraft acquired images of comet 67P/Churyumov-Gerasimenko (67P) and its surrounding dust coma starting from May 2014 until September 2016. In this paper we present methods and results from analysis of OSIRIS images regarding the dust outflow in the innermost coma of 67P. The aim is to determine the global dust outflow behaviour and place constraints on physical processes affecting particles in the inner coma. We study the coma region right above the nucleus surface, spanning from the nucleus centre out to a distance of about 50 km comet centric distance (approximately 25 average comet radii). We primarily adopt an approach used by Thomas and to study the dust outflow. We present the effects on azimuthally-averaged values of the dust reflectance of non-radial * Corresponding author.
Monthly Notices of the Royal Astronomical Society, 2016
Beginning in 2014 March, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) ... more Beginning in 2014 March, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras began capturing images of the nucleus and coma (gas and dust) of comet 67P/Churyumov-Gerasimenko using both the wide angle camera (WAC) and the narrow angle camera (NAC). The many observations taken since July of 2014 have been used to study the morphology, location, and temporal variation of the comet's dust jets. We analysed the dust monitoring observations shortly after the southern vernal equinox on 2015 May 30 and 31 with the WAC at the heliocentric distance R h = 1.53 AU, where it is possible to observe that the jet rotates with the nucleus. We found that the decline of brightness as a function of the distance of the jet is much steeper than the background coma, which is a first indication of sublimation. We adapted a model of sublimation of icy aggregates and studied the effect as a function of the physical properties of the aggregates (composition and size). The major finding of this paper was that through the sublimation of the aggregates of dirty grains (radius a between 5 and 50 μm) we were able to completely reproduce the radial brightness profile of a jet beyond 4 km from the nucleus. To reproduce the data, we needed to inject a number of aggregates between 8.5 × 10 13 and 8.5 × 10 10 for a = 5 and 50 μm, respectively, or an initial mass of H 2 O ice around 22 kg.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2017
We present a summary of the campaign of remote observations that supported the European Space Age... more We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov–Gerasimenko from before Rosetta's arrival until nearly the end of the mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively ‘well-behaved’ comet, typical of Jupiter family comets and with activity patterns that repeat from orbit to orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends—in this paper, we present a summary of the ground-based observations and early results, and point to many questions that will be a...
We report on recent efforts to characterize the zonal wind flow in the upper atmosphere of Titan ... more We report on recent efforts to characterize the zonal wind flow in the upper atmosphere of Titan from high resolution spectroscopic observations with the Very Large Telescope.
Comet C/2001 Q4 (NEAT) was observed at ESO (La Silla) for three consecutive nights at the beginni... more Comet C/2001 Q4 (NEAT) was observed at ESO (La Silla) for three consecutive nights at the beginning of May, 2004 at its closest approach to Earth. The observations consisted of quasi-simultaneous multi-wavelength exposures in the visible, near-IR and thermal-IR in order to study different properties of the solid component that are responsible for the scattering and emission of radiation in
A major discovery of ISO was the detection of water in the upper atmospheres of the four giant pl... more A major discovery of ISO was the detection of water in the upper atmospheres of the four giant planets and Titan (Feuchtgruber et al, 1997; Coustenis et al, 1998), implying the existence of external sources of water. This oxygen supply, which manifests itself also through the presence of CO2 and CO in these atmospheres, may have several sources: (i) a
Pits have been observed on many cometary nuclei mapped by spacecraft. It has been argued that com... more Pits have been observed on many cometary nuclei mapped by spacecraft. It has been argued that cometary pits are a signature of endogenic activity, rather than impact craters such as those on planetary and asteroid surfaces. Impact experiments and models cannot reproduce the shapes of most of the observed cometary pits, and the predicted collision rates imply that few of the pits are related to impacts. Alternative mechanisms like explosive activity have been suggested, but the driving process remains unknown. Here we report that pits on comet 67P/Churyumov-Gerasimenko are active, and probably created by a sinkhole process, possibly accompanied by outbursts. We argue that after formation, pits expand slowly in diameter, owing to sublimation-driven retreat of the walls. Therefore, pits characterize how eroded the surface is: a fresh cometary surface will have a ragged structure with many pits, while an evolved surface will look smoother. The size and spatial distribution of pits imply...
Disk averaged observations of several H2O far infrared lines in Titan’s atmosphere were performed... more Disk averaged observations of several H2O far infrared lines in Titan’s atmosphere were performed with the Herschel Space Observatory, as part of the guaranteed time key program "Water and related chemistry in the Solar System" (HssO, see Hartogh et al 2011). Two instruments were used: (i) HIFI, a heterodyne instrument (R~ 106 ) in the sub-millimeter, which measured the H2O(110-101) rotational transition at 557 GHz on June 10 and Dec. 31, 2010 (ii) PACS, a photoconductor spectrometer (R~103) which measured three water lines at 108.1, 75.4 and 66.4 microns on June 22, 2010. Additional PACS measurements at 66.4 microns on Dec. 15 and 22, 2010 and on July 09, 2011, do not show any significant line intensity variation with time, nor between the leading/trailing sides (i.e. longitude). Spectra were analyzed with a line-by-line radiative transfer code accounting for spherical geometry (Moreno et al. 2011). This model considers the H2O molecular opacity from JPL catalog (Pickett ...
In May 2006 comet 73P/SW3 passed at less than 0.1 AU from Earth providing us an unique opportunit... more In May 2006 comet 73P/SW3 passed at less than 0.1 AU from Earth providing us an unique opportunity for high spatial resolution study of its coma. This event was expected to be very interesting because the comet had broken apart in 3-4 fragments in 1996. The 2006 apparition has been even more interesting because the fragments produced in 1996, when
Astrophysical multi-wavelength studies of solar like G-type stars at several stages of their main... more Astrophysical multi-wavelength studies of solar like G-type stars at several stages of their main sequence lifetime indicate that our Sun may have had also undergone a highly active phase in its particle and radiation environment 3.5 - 4.5 Gyr ago. A detailed study of such solar like stars by the ROSAT and ASCA X-ray satellites show that the X-ray luminosity
ESA's Rosetta spacecraft was pointed towards the Deep Impact target comet Tempel 1 from 28 Ju... more ESA's Rosetta spacecraft was pointed towards the Deep Impact target comet Tempel 1 from 28 June to 14 July 2005. The OSIRIS cameras, the wide angle camera (WAC) and narrow angle camera (NAC) continuously observed the comet with high time resolution (down to less than a minute) around the impact on 4 July. The filter sets of the WAC were
In this work we use a mechanical dislocation program to analyze the fault geometries and depths a... more In this work we use a mechanical dislocation program to analyze the fault geometries and depths associated with a group of prominent lobate scarps in Mercury. We obtain depths of faulting of 30-40 km. This range overlaps with those previously obtained for Discovery Rupes and for two unnamed lobate scarps.
Mercurian lobate scarps are interpreted to be the surface expressions of thrust faults formed by ... more Mercurian lobate scarps are interpreted to be the surface expressions of thrust faults formed by planetary cooling and contraction, which deformed the crust down to the brittleductile transition (BOT) depth at the time of faulting. In this work we have used a forward modeling procedure in order to analyze the relation between scarp topography and fault geometries and depths associated with a group of prominent lobate scarps (Santa Maria Rupes and two unnamed scarps) located in the Kuiper region of Mercury for whi c h Earth-based radar altimetry is available. Also a backthrust associated with one of the lobate scarps has been included in this study. We have obtained best fits for depths of faulting between 30 and 39 km; the results are consistent with the previous results for other lobate scarps on Mercury. The so-derived fault depths have been used to calculate surface heat flows for the time of faulting, taking into account crustal heat sources and a heterogeneous surface temperature due to the variable insolation pattern. Deduced surface heat flows are between 19 and 39 mW m-2 for the Kuiper region, and between 22 and 43 mW m-2 for Discovery Rupes. Both BOT depths and heat flows are consistent with the predictions of thermal history models for the range of time relevant for scarp formation.
ESA’s Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian syst... more ESA’s Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian system in the 2030s, combining a suite of state-of-the-art instruments with an orbital tour tailored to maximise observing opportunities. We review the Jupiter science enabled by the JUICE mission, building on the legacy of discoveries from the Galileo, Cassini, and Juno missions, alongside ground- and space-based observatories. We focus on remote sensing of the climate, meteorology, and chemistry of the atmosphere and auroras from the cloud-forming weather layer, through the upper troposphere, into the stratosphere and ionosphere. The Jupiter orbital tour provides a wealth of opportunities for atmospheric and auroral science: global perspectives with its near-equatorial and inclined phases, sampling all phase angles from dayside to nightside, and investigating phenomena evolving on timescales from minutes to months. The remote sensing payload spans far-UV spectroscopy (50-210 nm), visible i...
The seasonal deposition and sublimation of CO constitute a major element in the Martian volatile ... more The seasonal deposition and sublimation of CO constitute a major element in the Martian volatile cycle. Here, we propose to use the shadow variations of the ice blocks at the foot of the steep scarps of the North Polar Layered Deposits (NPLDs) to infer the vertical evolution of the seasonal deposits at high polar latitudes. We conduct an experiment at a steep scarp centered at (85.0°N, 151.5°E). We show that the average thickness of the seasonal deposits due to snowfalls in Mars Year 31 is 0.97±0.13 m at Ls = 350.7° in late winter, which then gradually decreases in springtime. The large snow depth measured makes us wonder if snowfalls are more frequent and violent than previously thought. Meanwhile, we show that the average frost thickness due to direct condensation in Mars Year 31 reaches 0.64±0.18 m at Ls = 350.7° in late winter and quasi-linearly decreases towards the summer solstice. Combined, the total thickness of the seasonal cover in Mars Year 31 reaches 1.63±0.22 m at Ls = ...
The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) onboard the European Spac... more The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) onboard the European Space Agency's Rosetta spacecraft acquired images of comet 67P/Churyumov-Gerasimenko (67P) and its surrounding dust coma starting from May 2014 until September 2016. In this paper we present methods and results from analysis of OSIRIS images regarding the dust outflow in the innermost coma of 67P. The aim is to determine the global dust outflow behaviour and place constraints on physical processes affecting particles in the inner coma. We study the coma region right above the nucleus surface, spanning from the nucleus centre out to a distance of about 50 km comet centric distance (approximately 25 average comet radii). We primarily adopt an approach used by Thomas and to study the dust outflow. We present the effects on azimuthally-averaged values of the dust reflectance of non-radial * Corresponding author.
Monthly Notices of the Royal Astronomical Society, 2016
Beginning in 2014 March, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) ... more Beginning in 2014 March, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras began capturing images of the nucleus and coma (gas and dust) of comet 67P/Churyumov-Gerasimenko using both the wide angle camera (WAC) and the narrow angle camera (NAC). The many observations taken since July of 2014 have been used to study the morphology, location, and temporal variation of the comet's dust jets. We analysed the dust monitoring observations shortly after the southern vernal equinox on 2015 May 30 and 31 with the WAC at the heliocentric distance R h = 1.53 AU, where it is possible to observe that the jet rotates with the nucleus. We found that the decline of brightness as a function of the distance of the jet is much steeper than the background coma, which is a first indication of sublimation. We adapted a model of sublimation of icy aggregates and studied the effect as a function of the physical properties of the aggregates (composition and size). The major finding of this paper was that through the sublimation of the aggregates of dirty grains (radius a between 5 and 50 μm) we were able to completely reproduce the radial brightness profile of a jet beyond 4 km from the nucleus. To reproduce the data, we needed to inject a number of aggregates between 8.5 × 10 13 and 8.5 × 10 10 for a = 5 and 50 μm, respectively, or an initial mass of H 2 O ice around 22 kg.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2017
We present a summary of the campaign of remote observations that supported the European Space Age... more We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov–Gerasimenko from before Rosetta's arrival until nearly the end of the mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively ‘well-behaved’ comet, typical of Jupiter family comets and with activity patterns that repeat from orbit to orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends—in this paper, we present a summary of the ground-based observations and early results, and point to many questions that will be a...
We report on recent efforts to characterize the zonal wind flow in the upper atmosphere of Titan ... more We report on recent efforts to characterize the zonal wind flow in the upper atmosphere of Titan from high resolution spectroscopic observations with the Very Large Telescope.
Comet C/2001 Q4 (NEAT) was observed at ESO (La Silla) for three consecutive nights at the beginni... more Comet C/2001 Q4 (NEAT) was observed at ESO (La Silla) for three consecutive nights at the beginning of May, 2004 at its closest approach to Earth. The observations consisted of quasi-simultaneous multi-wavelength exposures in the visible, near-IR and thermal-IR in order to study different properties of the solid component that are responsible for the scattering and emission of radiation in
A major discovery of ISO was the detection of water in the upper atmospheres of the four giant pl... more A major discovery of ISO was the detection of water in the upper atmospheres of the four giant planets and Titan (Feuchtgruber et al, 1997; Coustenis et al, 1998), implying the existence of external sources of water. This oxygen supply, which manifests itself also through the presence of CO2 and CO in these atmospheres, may have several sources: (i) a
Pits have been observed on many cometary nuclei mapped by spacecraft. It has been argued that com... more Pits have been observed on many cometary nuclei mapped by spacecraft. It has been argued that cometary pits are a signature of endogenic activity, rather than impact craters such as those on planetary and asteroid surfaces. Impact experiments and models cannot reproduce the shapes of most of the observed cometary pits, and the predicted collision rates imply that few of the pits are related to impacts. Alternative mechanisms like explosive activity have been suggested, but the driving process remains unknown. Here we report that pits on comet 67P/Churyumov-Gerasimenko are active, and probably created by a sinkhole process, possibly accompanied by outbursts. We argue that after formation, pits expand slowly in diameter, owing to sublimation-driven retreat of the walls. Therefore, pits characterize how eroded the surface is: a fresh cometary surface will have a ragged structure with many pits, while an evolved surface will look smoother. The size and spatial distribution of pits imply...
Disk averaged observations of several H2O far infrared lines in Titan’s atmosphere were performed... more Disk averaged observations of several H2O far infrared lines in Titan’s atmosphere were performed with the Herschel Space Observatory, as part of the guaranteed time key program "Water and related chemistry in the Solar System" (HssO, see Hartogh et al 2011). Two instruments were used: (i) HIFI, a heterodyne instrument (R~ 106 ) in the sub-millimeter, which measured the H2O(110-101) rotational transition at 557 GHz on June 10 and Dec. 31, 2010 (ii) PACS, a photoconductor spectrometer (R~103) which measured three water lines at 108.1, 75.4 and 66.4 microns on June 22, 2010. Additional PACS measurements at 66.4 microns on Dec. 15 and 22, 2010 and on July 09, 2011, do not show any significant line intensity variation with time, nor between the leading/trailing sides (i.e. longitude). Spectra were analyzed with a line-by-line radiative transfer code accounting for spherical geometry (Moreno et al. 2011). This model considers the H2O molecular opacity from JPL catalog (Pickett ...
In May 2006 comet 73P/SW3 passed at less than 0.1 AU from Earth providing us an unique opportunit... more In May 2006 comet 73P/SW3 passed at less than 0.1 AU from Earth providing us an unique opportunity for high spatial resolution study of its coma. This event was expected to be very interesting because the comet had broken apart in 3-4 fragments in 1996. The 2006 apparition has been even more interesting because the fragments produced in 1996, when
Astrophysical multi-wavelength studies of solar like G-type stars at several stages of their main... more Astrophysical multi-wavelength studies of solar like G-type stars at several stages of their main sequence lifetime indicate that our Sun may have had also undergone a highly active phase in its particle and radiation environment 3.5 - 4.5 Gyr ago. A detailed study of such solar like stars by the ROSAT and ASCA X-ray satellites show that the X-ray luminosity
ESA's Rosetta spacecraft was pointed towards the Deep Impact target comet Tempel 1 from 28 Ju... more ESA's Rosetta spacecraft was pointed towards the Deep Impact target comet Tempel 1 from 28 June to 14 July 2005. The OSIRIS cameras, the wide angle camera (WAC) and narrow angle camera (NAC) continuously observed the comet with high time resolution (down to less than a minute) around the impact on 4 July. The filter sets of the WAC were
In this work we use a mechanical dislocation program to analyze the fault geometries and depths a... more In this work we use a mechanical dislocation program to analyze the fault geometries and depths associated with a group of prominent lobate scarps in Mercury. We obtain depths of faulting of 30-40 km. This range overlaps with those previously obtained for Discovery Rupes and for two unnamed lobate scarps.
Mercurian lobate scarps are interpreted to be the surface expressions of thrust faults formed by ... more Mercurian lobate scarps are interpreted to be the surface expressions of thrust faults formed by planetary cooling and contraction, which deformed the crust down to the brittleductile transition (BOT) depth at the time of faulting. In this work we have used a forward modeling procedure in order to analyze the relation between scarp topography and fault geometries and depths associated with a group of prominent lobate scarps (Santa Maria Rupes and two unnamed scarps) located in the Kuiper region of Mercury for whi c h Earth-based radar altimetry is available. Also a backthrust associated with one of the lobate scarps has been included in this study. We have obtained best fits for depths of faulting between 30 and 39 km; the results are consistent with the previous results for other lobate scarps on Mercury. The so-derived fault depths have been used to calculate surface heat flows for the time of faulting, taking into account crustal heat sources and a heterogeneous surface temperature due to the variable insolation pattern. Deduced surface heat flows are between 19 and 39 mW m-2 for the Kuiper region, and between 22 and 43 mW m-2 for Discovery Rupes. Both BOT depths and heat flows are consistent with the predictions of thermal history models for the range of time relevant for scarp formation.
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Papers by Luisa M. Lara