arXiv subjects

Edwin S. Kite

Publications and source records attributed to Edwin S. Kite.

At least 19 recordsLinked to original sources

arXiv2026

Doubling Sunlight for a Human Mars Base With Orbiting Solar Reflectors

The Sun's faintness at Mars' orbit makes producing energy, melting ice, and staying warm more difficult. Orbiting solar reflectors (OSRs) can augment sunlight at Mars, but the area of OSRs needed to double sunlight at a Mars base is not known. Here, we analyze Sun-synchronous Mars orbits to find the OSR area that doubles insolation to a Mars base. We show that the reflectors can deliver sunlight and maintain a stable orbit via attitude control and solar-sail propulsion, with no propellant. We also show that these Mars orbits can be reached via solar sailing from low Earth orbit, reducing delivery cost. Doubling sunlight is viable with an orbiting solar reflector areal density of $20 {\rm g/m^2}$, a 7-fold improvement over flight-proven solar sails. However, designing a spacecraft with low areal density, agile maneuverability (for accurate pointing), high tension in the sail membrane (to smooth wrinkles), and mass-manufacturability (to enable a constellation of reflectors) would be challenging. Still lower areal density of $<5 {\rm g/m^2}$ would be needed for more ambitious applications, such as sublimating the CO$_2$ ice at Mars' south pole to aid in terraforming.

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arXiv2026

The dark and featureless surface of rocky exoplanet LHS 3844 b from JWST mid-infrared spectroscopy

JWST has opened a new era in the study of rocky exoplanets, enabling direct characterization of their surfaces with mid-infrared spectroscopy. Different types of rock have distinct spectral features that are diagnostic of the chemical composition and other physical properties like surface texture. Measurements of these features can provide valuable clues about a planet's geologic history and interior processes. Here we report a JWST 5-12 micron thermal emission spectrum for the rocky exoplanet LHS 3844 b. It is best matched by a dark, low-silica surface, such as basalt or other olivine-rich materials. The spectrum rules out fresh powder surfaces; however, space weathering can darken the powders and make them more consistent with the data. The data also disfavor trace concentrations of CO$_2$ or SO$_2$ gas (with 5-sigma and 3-sigma upper limits of 100 mbar and 10 microbar, respectively). Taken together, these results are well fit by an old, space-weathered surface with no evidence of accumulated volcanic gases.

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arXiv2026

Evidence for an Atmosphere on the Ultra-Short Period super-Earth HD 3167 b

'Lava worlds'-Earth-sized planets hot enough (Teq >~ 1100 K) to melt their dayside silicate surfaces-have emerged as promising candidates for atmospheric detection and characterization. Thermal emission observations show an apparent dichotomy: the hottest lava worlds have colder daysides than the temperature of a maximally emitting bare rock, indicating the likely presence of thick and/or reflective atmospheres while the coldest ones do not. However, where in instellation flux this potential bifurcation occurs is uncertain. We present a JWST MIRI LRS eclipse of the ultra-short period (USP) lava world HD 3167 b (Teq = 1786 K, R = 1.6 Rearth, P = 0.96 d) that helps bridge this gap. We measure the white light eclipse depth to be 38 +/- 11 ppm, more than 5 sigma lower than the expected eclipse depth of a dark, maximally hot bare rock. We use this to derive a dayside brightness temperature that is best explained by the presence of an atmosphere that cools the dayside by reflecting incoming starlight and/or efficiently redistributing heat to the planet's nightside. An atmosphere is further compatible with the planet's slight under-density compared to an Earth-like composition. The corresponding dayside emission spectrum is not precise enough to constrain atmospheric composition, motivating follow-up spectroscopic observations with JWST NIRSpec. Lastly, we use our observation and existing data to refine key planetary parameters of the HD 3167 system. HD 3167 b is currently the least irradiated USP super-Earth with evidence for an atmosphere.

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arXiv2026

Atmospheric dynamics of IR-active particles released from Mars' surface

Surface release of radiatively active particles, with high infrared- (IR-)to-visible extinction ratios, has been proposed as a method of warming Mars. However, to warm Mars using aerosols, particles released locally must disperse globally. Here we provide an initial reference study in a plume tracking, dry Martian atmospheric model to address this question. The winds that transport aerosols respond to the aerosol's IR forcing, implying strong radiative-dynamical feedbacks (RDF). We investigate RDF from surface release of two particle compositions: carbon (graphene) and metal (Al). Self-lofting helps particles rise and spread locally and regionally, and the Hadley cell strengthens under warming, aiding latitudinal mixing. Within our model, Mars RDF enable engineered-aerosol warming. Warming is slightly greater for three-dimensional vs. 1D-models and also depends on spectral resolution of radiative transfer. We assess implications for Mars warming. Many open atmospheric science questions remain, including the role of agglomeration, dry-deposition rate uncertainty, and modeling water cycle feedbacks.

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arXiv2026

Modelling the long-term impacts of artificial warming on the Martian water cycle and surface ice distribution

Recent papers by Ansari et al. (2024, Science Advances 10, eadn4650) and Richardson et al. (2025, arXiv eprint 2504.01455) have suggested that global warming of the Martian surface ('terraforming') by 35 K to sustain local habitats above the melting point of water could be achieved through the injection of engineered aerosols into the Martian atmosphere. Using the MarsWRF 3D Global Climate Model, we investigate how artificial warming of Mars through engineered aerosol release would affect the planetary water cycle and the distribution of the major surface ice reservoirs. Within our model framework, every 20 K of global warming induces a tenfold increase in atmospheric water vapour content due to sublimation of H2O ice from the North Polar Cap. This increases the potency of cloud radiative feedbacks which induces nighttime warming (~5-10 K) at low latitudes, but daytime cooling (up to 40 K) in the winter midlatitudes. Water is transferred from the edge of the North Polar Cap to the South Polar Cap and there is minor destabilisation of shallow northern midlatitude subsurface ice. As a result, seasonal sublimation of H2O ice from the South Pole has an increased impact on the global water cycle. These changes persist on Mars at least decades after loading of the atmosphere with engineered aerosols ceases. Our model is limited by the gaps in our knowledge of present-day Martian weather and climate, and of the microphysics and radiative properties of candidate warming agents. Much more data is therefore needed before warming Mars could become feasible.

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arXiv2025

The Cosmic Shoreline Revisited: A Metric for Atmospheric Retention Informed by Hydrodynamic Escape

The "cosmic shoreline," a semi-empirical relation that separates airless worlds from worlds with atmospheres as proposed by K. J. Zahnle & D. C. Catling, is now guiding large-scale JWST surveys aimed at detecting rocky exoplanet atmospheres. We expand upon this framework by revisiting the shoreline using existing hydrodynamic escape models applied to Earth-like, Venus-like, and steam atmospheres for rocky exoplanets, and we estimate energy-limited escape rates for CH4 atmospheres. We determine the critical instellation required for atmospheric retention by calculating time-integrated atmospheric mass loss. Our analysis introduces a new metric for target selection in the Rocky Worlds Director's Discretionary Time and refines expectations for rocky planet atmosphere searches. Exploring initial volatile inventory ranging from 0.01% to 1% of planetary mass, we find that its variation prevents the definition of a unique clear-cut shoreline, though nonlinear escape physics can reduce this sensitivity to initial conditions. Additionally, uncertain distributions of high-energy stellar evolution and planet age further blur the critical instellations for atmospheric retention, yielding broad shorelines. Hydrodynamic escape models find atmospheric retention is markedly more favorable for higher-mass planets orbiting higher-mass stars, with carbon-rich atmospheres remaining plausible for 55 Cancri e despite its extreme instellation. We caution that our estimates are sensitive to processes with poorly understood dynamics, such as atomic line cooling. Finally, we illustrate how density measurements can be used to statistically test the existence of the cosmic shorelines, emphasizing the need for more precise mass and radius measurements.

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arXiv2025

The JWST Rocky Worlds DDT Program reveals GJ 3929b to likely be a bare rock

We report first results from the JWST Rocky Worlds Director's Discretionary Time program. Two secondary eclipses of the terrestrial exoplanet GJ 3929b were recently observed using MIRI photometric imaging at 15 um. We present a reduction of these data using the updated SPARTA pipeline. We also refine the planet mass, radius, and predicted time of secondary eclipse using a new sector of TESS data and new, high-precision radial velocities from the MAROON-X spectrograph. For the two JWST observations, we recover secondary eclipse depths of 177+47-45ppm and 143+34-35ppm at times consistent with a nearly circular orbit, as expected from the radial velocity data. A joint fit of the two visits yields a dayside brightness temperature Tp,dayside = 782+/-79K for GJ 3929b, which is consistent with the maximum brightness temperature Tmax = 737+/-14K for a bare, black rock (i.e., assuming zero Bond albedo and no heat redistribution). These results rule out CO2-rich atmospheres thicker than 100mbar at >3sigma, suggesting that GJ 3929b has lost any significant secondary atmosphere. The radial velocity data also indicate two additional non-transiting planets in the system: a previously-identified planet in a 15.0d orbit, and a newly-identified planet candidate in a 6.1d orbit.

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arXiv2025

The Role of Tectonic Luck in Long-Term Habitability of Abiotic Earth-like Planets

Carbonate-silicate weathering feedback is thought to stabilize Earth's climate on geologic timescales. If climate warms, faster mineral dissolution and increased rainfall speed up weathering, increasing CO2 drawdown and opposing the initial warming. Limits to where this feedback might operate on terrestrial exoplanets with N2-O2-CO2-H2O atmospheres are used to define the 'habitable zone'-the range of orbits around a star where liquid water can be stable on a planet's surface. However, the impacts on long-term habitability of randomly varying volcanic outgassing, tectonic collisions, and tectonic parameters (e.g., number of continental plates, size of plates, plate velocity) remain poorly understood. In this work, we present an idealized and broadly-applicable quasi-2D model of the long-term climate stability of abiotic Earth-twins. The model tracks atmospheric CO2 as 'disks' collide, promoting uplift and supplying new weatherable minerals through erosion. Without resupply, soils become less weatherable and the feedback's strength wanes, making a planet susceptible to catastrophic warming events or hard snowballs where the surface becomes frozen over. We find that tectonic uplift spurred by continental collisions cannot be the sole supplier of weatherable minerals within our model framework, as such climates either become uninhabitably hot (for complex life) as soils become leached of weatherable minerals or experience extreme swings in temperature over short timescales. This conclusion is strengthened when taking into account the destabilizing effects of outgassing variability and increasing stellar luminosity. In addition to frequent collisions, other resupply mechanisms for weatherable minerals, such as wind-driven dust transport, glacial erosion, and/or seafloor weathering, are likely required for long-term stability on Earth-like terrestrial exoplanets.

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arXiv2025

Population-level Hypothesis Testing with Rocky Planet Emission Data: A Tentative Trend in the Brightness Temperatures of M-Earths

Determining which rocky exoplanets have atmospheres, and why, is a key goal for the James Webb Space Telescope. So far, emission observations of individual rocky exoplanets orbiting M stars (M-Earths) have not provided definitive evidence for atmospheres. Here, we synthesize emission data for M-Earths and find a trend in measured brightness temperatures (ratioed to its theoretical maximum value) as a function of instellation. However, the statistical evidence of this trend is dependent on the choice of stellar model, and we consider its identification tentative. We show that this trend can be explained by either the onset of thin/tenuous (<1 bar) CO2-rich atmospheres on colder worlds, or a population of bare rocks with stronger space weathering and/or coarser regolith on closer-in worlds. Such grain coarsening may be caused by sintering near the melting point of rock or frequent volcanic resurfacing. Furthermore, we highlight considerations when testing rocky planet hypotheses at the population level, including the choice of instrument, stellar modeling, and how brightness temperatures are derived. We also find that fresh (unweathered) fine-grained surfaces can serve as a false positive to the detection of moderate atmospheric heat redistribution through eclipse observations. However, we argue that such surfaces are unlikely given the ubiquity of space weathering in the Solar System, the low albedo of Solar System airless bodies, and the high stellar wind environments of M-Earths. Emission data from a larger sample of M-Earths will be able to confirm or reject this tentative trend and diagnose its cause through spectral characterization.

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arXiv2025

Extreme Weather Variability on Hot Rocky Exoplanet 55 Cancri e Explained by Magma Temperature-Cloud Feedback

Observations of the hot rocky exoplanet 55 Cancri e report significant but unexplained variability in brightness across visible and infrared bands, e.g., on sub-weekly timescales, its mid-infrared brightness temperature fluctuates by approximately 1400 K (with hundreds of Kelvin uncertainty). We propose a magma temperature-cloud feedback as a potential explanation that relies on the planet's atmosphere and surface. In this feedback, under cloud-free conditions, stellar radiation heats surface magma, releasing silicate vapor that condenses into clouds. Once formed, these clouds attenuate stellar insolation, thereby cooling the surface, reducing vapor supply, and decreasing cloudiness. A time lag between surface temperature increase and cloud formation, likely due to lagged atmospheric transport of cloud-forming vapor, enables self-sustained oscillations in surface temperature and cloudiness. These oscillations manifest as variations in both the planet's thermal emission and reflected starlight, causing variability in secondary eclipse depths across wavelengths without significantly affecting the transit depth. Using a simple model, we find that diverse planetary parameters can reproduce the observed infrared brightness variability. We also demonstrate that brightness at different wavelengths can oscillate out of phase, consistent with recent observations by the James Webb Space Telescope. Additionally, we propose that time-varying and spatially non-uniform cloud cover can result in changing amplitude and phase offset of the planet's phase curve, potentially explaining observations. Finally, we discuss observational strategies to test this proposed mechanism on 55 Cancri e. If confirmed, these observable ocean-atmosphere dynamics on exoplanets would provide valuable insights into the composition, evolution, and long-term fate of rocky planet volatiles.

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arXiv2025

Mars' Young Sedimentary Rocks: Early thinning, late persistence, diachronous boundaries, and a regional dichotomy

Mars' sedimentary rocks record Gyrs of environmental change. New data enable the first global analysis of paleo-environment relevant physical properties of these rocks, including layer thickness and accumulation rate. We find that layer thicknesses of post-3.5 Ga sedimentary rocks across the Martian surface show coherent variations at ~1000 km-scale that are inconsistent with simple volcanic and climatic hypotheses for formation, which are consistent with global compositional homogeneity at orbital scales. These data, in combination with new analyses of outcrop age and total rock volume demonstrate a global decrease in layer thickness that predates the eventual drop off in preserved sedimentary rock volume per Myr. The new constraints confirm a diachronous transition in Mars' global sedimentary rock record while also highlighting a regional dichotomy in young sedimentary rock deposits that has not been quantified before.

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arXiv2025

The transmission spectrum of the potentially rocky planet L 98-59 c

We present observations of the 1.35+/-0.07 Earth-radius planet L 98-59 c, collected using Wide Field Camera 3 on the Hubble Space Telescope. L 98-59 is a nearby (10.6 pc), bright (H=7.4 mag), M3V star that harbors three small, transiting planets. As one of the closest known transiting multi-planet systems, L 98-59 offers one of the best opportunities to probe and compare the atmospheres of rocky planets that formed in the same stellar environment. We measured the transmission spectrum of L 98-59 c and the extracted spectrum showed marginal evidence (2.1σ) for wavelength-dependent transit depth variations that could indicate the presence of an atmosphere. We forward-modeled possible atmospheric compositions of the planet based on the transmission spectrum. Although L 98-59 was previously thought to be a fairly quiet star, we have seen evidence for stellar activity, and therefore we assessed a scenario where the source of the signal originates with inhomogeneities on stellar surface. We also see a correlation between transits of L 98-59 c and L 98-59 b collected 12.5 hours apart, which is suggestive (but at <2σ confidence) of a contaminating component from the star impacting the exoplanet spectrum. While intriguing, our results are inconclusive and additional data is needed to verify any atmospheric signal. Fortunately, additional data has been collected from both HST and JWST. Should this result be confirmed with additional data, L 98-59 c would be the first planet smaller than two Earth-radii with a detected atmosphere.

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arXiv2024

No Thick Atmosphere on the Terrestrial Exoplanet Gl 486b

A primary science goal for JWST is to detect and characterize the atmospheres of terrestrial planets orbiting M dwarfs (M-Earths). The existence of atmospheres on M-Earths is highly uncertain because their host stars' extended history of high XUV irradiation may act to completely remove their atmospheres. We present two JWST secondary eclipse observations of the M-Earth Gl 486b (also known as GJ 486b) between 5-12 $μ$m. We combined these observations with a precise analysis of the host star parameters to derive a planetary dayside temperature of $T_{p}=865 \pm 14$ K. We compared this temperature to the maximum expected temperature for a zero albedo, zero heat redistribution bare rock and derived a temperature ratio of $R=\frac{T_{p,dayside}}{T_{p,max}}=0.97 \pm 0.01$. This value is consistent with an airless body with a slight non-zero albedo or a thin atmosphere with $<1$% H$_{2}$O or $<1$ ppm CO$_{2}$. However, it is inconsistent with an Earth- or Venus-like atmosphere, and the spectrum shows no clear emission or absorption features. Additionally, our observations are inconsistent with the water-rich atmospheric scenario allowed by previous transit observations and suggest the transmission spectrum was instead shaped by stellar contamination (Moran et al. 2023). Given the potential for atmospheric escape throughout the system's $\geq6.6$-Gyr lifetime (Diamond-Lowe et al. 2024), we conclude that the observations are likely best explained by an airless planet. This result is the most precise measurement yet of terrestrial exoplanet thermal emission with JWST, which places a strong constraint on the position of the "Cosmic Shoreline" between airless bodies and those with atmospheres.

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arXiv2024

Feasibility of keeping Mars warm with nanoparticles

One-third of Mars' surface has shallow-buried H$_2$O, but it is currently too cold for use by life. Proposals to warm Mars using greenhouse gases require a large mass of ingredients that are rare on Mars' surface. However, we show here that artificial aerosols made from materials that are readily available at Mars-for example, conductive nanorods that are ~9 $μ$m long-could warm Mars >5 $\times$ 10$^3$ times more effectively than the best gases. Such nanoparticles forward-scatter sunlight and efficiently block upwelling thermal infrared. Similar to the natural dust of Mars, they are swept high into Mars' atmosphere, allowing delivery from the near-surface. For a particle lifetime of 10 years, two climate models indicate that sustained release at 30 liters/sec would globally warm Mars by $\gtrsim$30 K and start to melt the ice. Therefore, if nanoparticles can be made at scale on (or delivered to) Mars, then the barrier to warming of Mars appears to not be as high as previously thought.

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arXiv2024

JWST Thermal Emission of the Terrestrial Exoplanet GJ 1132b

We present thermal emission measurements of GJ 1132b spanning 5--12 um obtained with the Mid-Infrared Instrument Low-Resolution Spectrometer (MIRI/LRS) on the James Webb Space Telescope (JWST). GJ 1132b is an M-dwarf rocky planet with Teq=584 K and an orbital period of 1.6 days. We measure a white-light secondary eclipse depth of 140+/-17 ppm, which corresponds to a dayside brightness temperature of Tp,dayside= 709+/-31 K using improved star and planet parameters. This measured temperature is only 1 sigma below the maximum possible dayside temperature of a bare rock (i.e., assuming a zero albedo planet with no heat redistribution, Tmax = 746+14/-11 K). The emission spectrum is consistent with a featureless blackbody, which agrees with a wide range of possible surface compositions. By comparing forward models to the dayside emission spectrum, we rule out Earth-thickness (P ~ 1 bar) atmospheres with at least 1% H2O, atmospheres of any modeled thickness (10^-4 -- 10^2 bar) that contain at least 1% CO2, and thick, Venus-like atmospheres (P>~100 bar) with at least 1 ppm CO2 or H2O. We therefore conclude that GJ 1132b likely does not have a significant atmosphere. This finding supports the concept of a universal 'Cosmic Shoreline' given the high level of bolometric and XUV irradiation received by the planet.

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arXiv2024

An Earth-sized Planet on the Verge of Tidal Disruption

TOI-6255~b (GJ 4256) is an Earth-sized planet (1.079$\pm0.065$ $R_\oplus$) with an orbital period of only 5.7 hours. With the newly commissioned Keck Planet Finder (KPF) and CARMENES spectrographs, we determined the planet's mass to be 1.44$\pm$0.14 $M_{\oplus}$. The planet is just outside the Roche limit, with $P_{\rm orb}/P_{\rm Roche}$ = 1.13 $\pm0.10$. The strong tidal force likely deforms the planet into a triaxial ellipsoid with a long axis that is $\sim$10\% longer than the short axis. Assuming a reduced stellar tidal quality factor $Q_\star^\prime \approx10^7$, we predict that tidal orbital decay will cause TOI-6255 to reach the Roche limit in roughly 400 Myr. Such tidal disruptions may produce the possible signatures of planet engulfment that have been on stars with anomalously high refractory elemental abundances compared to its conatal binary companion. TOI-6255 b is also a favorable target for searching for star-planet magnetic interactions, which might cause interior melting and hasten orbital decay. TOI-6255 b is a top target (Emission Spectroscopy Metric of about 24) for phase curve observations with the James Webb Space Telescope.

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arXiv2024

Multiple overspill flood channels from young craters require surface melting and hundreds of meters of mid-latitude ice late in Mars history

Mars' tadpole craters are small, young craters whose crater rims are incised by one or more exit breaches but lack visible inlets. The tadpole forming climate records the poorly understood drying of Mars since the Early Hesperian. A third of tadpole craters have multiple breaches, therefore a process is needed that was able to generate crater rim incision in multiple locations. We use HiRISE data for four multiple breach tadpole craters to measure their crater fill, rims, and exit breaches. We compare these measurements and other data to our calculations of liquid water supply by rain, surface melting, groundwater discharge, and basal ice sheet melting to discriminate between four proposed formation hypotheses for tadpole breaches, favoring scenarios with ice-filled craters and supraglacial melting. We conclude that multiple breach tadpole craters record hundreds of meters of mid-latitude ice and climate conditions enabling intermittent melting in the Late Hesperian and Amazonian, suggesting that liquid water on Mars has been available in association with water ice for billions of years.

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arXiv2023

Why are Mountaintops Cold? The Transition of Surface Lapse Rate on Dry Planets

Understanding surface temperature is important for habitability. Recent work on Mars has found that the dependence of surface temperature on elevation (surface lapse rate) converges to zero in the limit of a thin CO2 atmosphere. However, the mechanisms that control the surface lapse rate are still not fully understood. It remains unclear how the surface lapse rate depends on both greenhouse effect and surface pressure. Here, we use climate models to study when and why "mountaintops are cold". We find the tropical surface lapse rate increases with the greenhouse effect and with surface pressure. The greenhouse effect dominates the surface lapse rate transition and is robust across latitudes. The pressure effect is important at low latitudes in moderately opaque atmospheres. A simple model provides insights into the mechanisms of the transition. Our results suggest that topographic cold-trapping may be important for the climate of arid planets.

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