Atmospheric Loss Research Articles

Assessment of static and dynamic deformations of the orbital station shell by a system of integrating fiber-optic sensors

The problem of safe functioning of space vehicles is under investigation. Spacecraft safety is essentially affected by the impact of fragments of space debris and meteorites. Impact of small particle can lead to a perforation of the structure of a spacecraft or the Space station. The impact can cause formation of a perforation and gradual loss of atmosphere. Under these conditions, it is crucial detecting the point of perforation and take the measures of precaution for the loss of the internal atmosphere. Practically all known methods for testing the integrity of ground-based structures, aircrafts and other complex technogenic objects are inapplicable for solving similar problems of monitoring the spacecraft condition during a spaceflight. To solve this problem, the integrating fiber-optic sensors (IFOS)-based system for monitoring vibration deformation parameters of spacecraft housings’ surfaces is proposed, which can be developed and implemented in the shortest possible time. Mathematical modeling and laboratory studies have confirmed the possibility of using the Integrating fiber-optic sensors system for assessing the dynamic and static parameters of extended structures.

The Activity of Stars with Planetary Systems and Its Impact on the Loss of Atmosphere by Hot Exoplanets

The Activity of Stars with Planetary Systems and Its Impact on the Loss of Atmosphere by Hot Exoplanets

Hovering UAV-Based FSO Communications: Channel Modelling, Performance Analysis, and Parameter Optimization

Relay-assisted free-space optical (FSO) communication systems are exploited as a means to mitigate the limiting effects of the turbulence induced atmospheric scintillation. However, conventional ground relays are stationary, and their optimal placement is not always feasible. Due to their mobility and flexibility, unmanned aerial vehicles (UAVs) provide new opportunities for FSO relaying systems. In this paper, a hovering UAV-based serial FSO decode-and-forward relaying system is investigated. In the channel modelling for such a system, four types of impairments (i.e., atmospheric loss, atmospheric turbulence, pointing error, and link interruption due to angle-of-arrival fluctuation) are considered. Based on the proposed channel model, a tractable expression for the probability density function of the total channel gain is obtained. Closed-form expressions of the link outage probability and end-to-end outage probability are derived. Asymptotic outage performance bounds for each link and the overall system are also presented to reveal insights into the impacts of different impairments. To improve system performance, we optimize the beam width, field-of-view and UAVs' locations. Numerical results show that the derived theoretical expressions are accurate to evaluate the outage performance of the system. Moreover, the proposed optimization schemes are efficient and can improve performance significantly.

Atmospheric sound transmission loss uncertainties induced by sea roughness

This work presents a numerical study conducted on atmospheric sound propagation over sea. In particular, it focuses on the sound pressure level prediction uncertainties induced by the water surface roughness. To quantify these uncertainties, the generalized terrain parabolic equation (GTPE) is used to model sound propagation above water surfaces at different sea states. Water roughness is pseudo-randomly generated using an ocean wave spectrum. The GTPE predictions are compared with those obtained using the Crank-Nicholson parabolic equation (CNPE) solver. When using the CNPE the sea surface is flat and has a surface impedance equivalent to that of a rough surface. The use of the GTPE is less computationally efficient but provides insight on the detectability of an acoustic source at sea. This work presents relationships between fully developed sea states (up to sea state 4) and the uncertainties on sound pressure level predictions at distances up to 500 m from the source. These relationships are presented for typical diurnal and nocturnal thermal gradients and for different elevations from the water surface.

Grain Growth in Escaping Atmospheres: Implications for the Radius Inflation of Super-Puffs

Abstract Super-puffs—low-mass exoplanets with extremely low bulk density—are attractive targets for exploring their atmospheres and formation processes. Recent studies suggested that the large radii of super-puffs may be caused by atmospheric dust entrained in the escaping atmospheres. In this study, we investigate how the dust grows in escaping atmospheres and influences the transit radii using a microphysical model of grain growth. Collision growth is efficient in many cases, hindering the upward transport of dust via enhanced gravitational settling. We find that the dust abundance in the outflow hardly exceeds the Mach number at the dust production region. Thus, dust formed in the upper atmospheres, say at P ≲ 10−5 bar, is needed to launch a dusty outflow with a high dust abundance. With sufficiently high dust production altitudes and rates, the dusty outflow can enhance the observable radius by a factor of ∼2 or even more. We suggest that photochemical haze is a promising candidate of high-altitude dust that can be entrained in the outflow. We also compute the synthetic transmission spectra of super-puff atmospheres and demonstrate that the dusty outflow produces a broad spectral slope and obscures molecular features, in agreement with featureless spectra recently reported for several super-puffs. Lastly, using an interior structure model, we suggest that the atmospheric dust could drastically enhance the observable radius only for planets in a narrow mass range of ∼2–5 M ⊕, in which the boil-off tends to cause total atmospheric loss. This may explain why super-puffs are uncommon despite the suggested universality of photochemical hazes.

Deep space optical communications (DSOC) downlink simulation with varying PPM order

During the course of a typical deep space mission like the Mars Earth mission, there exist a wide range of operating points, due to the different changes in geometry that consequently cause different link budgets in terms of received signal and noise power. These changes include distance range, Sun-Earth-Probe angle, zenith angle and atmospheric conditions. The different operating points, with different losses (background noise, pointing losses and atmospheric losses), lead to different capacities and data rates over the course of a typical deep space mission. Consequently, different engineering parameters are adjusted and optimized to combat some of these varying losses in order to get acceptable data rates and bit error probabilities. This is a useful reason to analyze and simulate various operating conditions that occur with the varying spatial orbital time periods of the resulting received signal power level, noise power level, capacity, data rates and bit error probabilities. This paper details results of simulations of typical deep space optical communication link operation.

Role of Criegee intermediates in the formation of sulfuric acid at a Mediterranean (Cape Corsica) site under influence of biogenic emissions

Abstract. Reaction of stabilized Criegee intermediates (SCIs) with SO2 was proposed as an additional pathway of gaseous sulfuric acid (H2SO4) formation in the atmosphere, supplementary to the conventional mechanism of H2SO4 production by oxidation of SO2 in reaction with OH radicals. However, because of a large uncertainty in mechanism and rate coefficients for the atmospheric formation and loss reactions of different SCIs, the importance of this additional source is not well established. In this work, we present an estimation of the role of SCIs in H2SO4 formation at a western Mediterranean (Cape Corsica) remote site, where comprehensive field observations including gas-phase H2SO4, OH radicals, SO2, volatile organic compounds (VOCs) and aerosol size distribution measurements were performed in July–August 2013 as a part of the project ChArMEx (Chemistry-Aerosols Mediterranean Experiment). The measurement site was under strong influence of local emissions of biogenic volatile organic compounds, including monoterpenes and isoprene generating SCIs in reactions with ozone, and, hence, presenting an additional source of H2SO4 via SO2 oxidation by the SCIs. Assuming the validity of a steady state between H2SO4 production and its loss by condensation on existing aerosol particles with a unity accommodation coefficient, about 90 % of the H2SO4 formation during the day could be explained by the reaction of SO2 with OH. During the night the oxidation of SO2 by OH radicals was found to contribute only about 10 % to the H2SO4 formation. The accuracy of the derived values for the contribution of OH + SO2 reaction to the H2SO4 formation is limited mostly by a large, at present factor of 2, uncertainty in the OH + SO2 reaction rate coefficient. The contribution of the SO2 oxidation by SCIs to the H2SO4 formation was evaluated using available measurements of unsaturated VOCs and steady-state SCI concentrations estimated by adopting rate coefficients for SCI reactions based on structure–activity relationships (SARs). The estimated concentration of the sum of SCIs was in the range of (1–3) × 103 molec. cm−3. During the day the reaction of SCIs with SO2 was found to account for about 10 % and during the night for about 40 % of the H2SO4 production, closing the H2SO4 budget during the day but leaving unexplained about 50 % of the H2SO4 formation during the night. Despite large uncertainties in used kinetic parameters, these results indicate that the SO2 oxidation by SCIs may represent an important H2SO4 source in VOC-rich environments, especially during nighttime.

Radioactive Planet Formation

Abstract Young stellar objects are observed to have large X-ray fluxes and are thought to produce commensurate luminosities in energetic particles (cosmic rays). This particle radiation, in turn, can synthesize short-lived radioactive nuclei through spallation. With a focus on 26Al, this paper estimates the expected abundances of radioactive nuclei produced by spallation during the epoch of planet formation. In this model, cosmic rays are accelerated near the inner truncation radii of circumstellar disks, r X ≈ 0.1 au, where intense magnetic activity takes place. For planets forming in this region, radioactive abundances can be enhanced over the values inferred for the early solar system (from meteoritic measurements) by factors of ∼10−20. These short-lived radioactive nuclei influence the process of planet formation and the properties of planets in several ways. The minimum size required for planetesimals to become fully molten decreases with increasing levels of radioactive enrichment, and such melting leads to loss of volatile components, including water. Planets produced with an enhanced radioactive inventory have significant internal luminosity, which can be comparable to that provided by the host star; this additional heating affects both atmospheric mass loss and chemical composition. Finally, the habitable zone of red dwarf stars is coincident with the magnetic reconnection region, so that planets forming at those locations will experience maximum exposure to particle radiation and subsequent depletion of volatiles.

Martian Crustal Field Influence on O+ and O2+ Escape as Measured by MAVEN

AbstractMartian crustal magnetic fields influence the solar wind interaction with Mars in a way that is not fully understood. In some locations, crustal magnetic fields act as “mini‐magnetospheres,” shielding the planet's atmosphere, while in other locations they act as channels for enhanced energy input and particle escape. The net effect of this system is not intuitively clear, but previous modeling studies have suggested that crustal fields likely decrease global ion escape from Mars. In this study, we use data from the Mars Atmosphere and Volatile EvolutioN spacecraft to analyze how crustal magnetic fields influence both global and local ion escape at Mars. We find that crustal fields only increase ion escape if ions are not bound tightly to the magnetic field. Specifically, ion escape is increased only if closed magnetic fields trap 35% or less of energized oxygen ions. In any other case, crustal fields decrease both global and local ion escape by as much as 40% and 80%, respectively. This suggests that the presence of crustal magnetic fields has had a moderate impact on atmospheric ion loss throughout Martian history, potentially influencing the planet's atmospheric evolution and habitability.

Characterization and ozone formation potential (OFP) of non-methane hydrocarbons under the condition of chemical loss in Guangzhou, China

The conventional analytical studies to determine ozone formation potential (OFP) and potential sources currently ignore the destruction of non-methane hydrocarbons (NMHCs) during atmospheric transport, namely chemical loss. The chemical loss of NMHCs was estimated using photochemical age based on the online observation data of NMHCs from the Guangzhou Panyu Atmospheric Composition Station (GPACS) in the Pearl River Delta (PRD) during summer (June, July, and August) and autumn (September, October, and November) - two seasons favorable to the photochemical generation of ozone - of 2012. Subsequently, the composition characteristics, OFPs, and potential sources of the NMHCs were analyzed under the condition of atmospheric photochemical loss. The results showed that the initial mixing ratios of NMHCs (i.e., the mixing ratios after discharge from emission sources, before they experience any significant atmospheric chemical reaction), during summer (37.30 ppbv) and autumn (41.62 ppbv) were 6.90 ppbv and 5.98 ppbv higher than the observed, respectively. Four maximum incremental reactivity (MIR) scales were used to calculate the OFP for NMHCs seasonal losses. The obtained OFPs were 62.67 ppbv, 73.05 ppbv, 73.31 ppbv, and 68.51 ppbv in summer and 47.71 ppbv, 55.54 ppbv, 56.12 ppbv, and 52.68 ppbv in autumn as calculated by the respective MIR scales. Both the MIR and the propylene-equivalent mixing ratio reflect the reactivity of various NMHC species to a certain extent. Isoprene, toluene, and xylene were found key species for controlling ozone. Based on the source analysis of the initial mixing ratio of NMHCs, vehicle emissions and solvent consumption were the major sources in Guangzhou.

Atmospheric Loss of Atomic Oxygen during Proton Aurorae on Mars

—For the first time, the calculations of the penetration of protons of the undisturbed solar wind into the daytime atmosphere of Mars due to charge exchange in the extended hydrogen corona (Shematovich et al., 2021) are used allowing us to determine self-consistently the sources of suprathermal oxygen atoms, as well as their kinetics and transport. An additional source of hot oxygen atoms—collisions accompanied by the momentum and energy transfer from the flux of precipitating high-energy hydrogen atoms to atomic oxygen in the upper atmosphere of Mars—was included in the Boltzmann kinetic equation, which was solved with the Monte-Carlo kinetic model. As a result, the population of the hot oxygen corona of Mars has been estimated; and it has been shown that the proton aurorae are accompanied by the atmospheric loss of atomic oxygen, which is evaluated within a range of (3.5–5.8) × 107 cm–2 s–1. It has been shown that the exosphere becomes populated with a substantial amount of suprathermal oxygen atoms with kinetic energies up to the escape energy, 2 eV. The atomic oxygen loss rate caused by a sporadic source in the Martian atmosphere—the precipitation of energetic neutral atoms of hydrogen (H‑ENAs) during proton aurorae at Mars—was estimated by the self-consistent calculations according to a set of the Monte-Carlo kinetic models. These values turned out be comparable to the atomic oxygen loss supported by a regular source—the exothermic photochemical reactions (Groeller et al., 2014; Jakosky et al., 2018). It is currently supposed that the atmospheric loss of Mars due to the impact of the solar wind plasma and, in particular, the fluxes of precipitating high-energy protons and hydrogen atoms during solar flares and coronal mass ejections may play an important role in the loss of the neutral atmosphere on astronomic time scales (Jakosky et al., 2018).

Transit detection of the long-period volatile-rich super-Earth ν2 Lupi d with CHEOPS

Exoplanets transiting bright nearby stars are key objects for advancing our knowledge of planetary formation and evolution. The wealth of photons from the host star gives detailed access to the atmospheric, interior and orbital properties of the planetary companions. ν2 Lupi (HD 136352) is a naked-eye (V = 5.78) Sun-like star that was discovered to host three low-mass planets with orbital periods of 11.6, 27.6 and 107.6 d via radial-velocity monitoring1. The two inner planets (b and c) were recently found to transit2, prompting a photometric follow-up by the brand new Characterising Exoplanets Satellite (CHEOPS). Here, we report that the outer planet d is also transiting, and measure its radius and mass to be 2.56 ± 0.09 R⊕ and 8.82 ± 0.94 M⊕, respectively. With its bright Sun-like star, long period and mild irradiation (~5.7 times the irradiation of Earth), ν2 Lupi d unlocks a completely new region in the parameter space of exoplanets amenable to detailed characterization. We refine the properties of all three planets: planet b probably has a rocky mostly dry composition, while planets c and d seem to have retained small hydrogen–helium envelopes and a possibly large water fraction. This diversity of planetary compositions makes the ν2 Lupi system an excellent laboratory for testing formation and evolution models of low-mass planets. Three planets orbit the Sun-like star ν2 Lupi. CHEOPS data show that all of them are transiting and show remarkable diversity. In particular, dry and gas-poor inner planet b has experienced extensive atmospheric loss, while planets c and d are water rich and have a small gaseous envelope of primordial origin.

Isotopic fractionation of water and its photolytic products in the atmosphere of Mars

The current Martian atmosphere is about five times more enriched in deuterium than Earth’s, providing direct testimony that Mars hosted vastly more water in its early youth than nowadays. Estimates of the total amount of water lost to space from the current mean D/H value depend on a rigorous appraisal of the relative escape between deuterated and non-deuterated water. Isotopic fractionation of D/H between the lower and the upper atmospheres of Mars has been assumed to be controlled by water condensation and photolysis, although their respective roles in influencing the proportions of atomic D and H populations have remained speculative. Here we report HDO and H2O profiles observed by the Atmospheric Chemistry Suite (ExoMars Trace Gas Orbiter) in orbit around Mars that, once combined with expected photolysis rates, reveal the prevalence of the perihelion season for the formation of atomic H and D at altitudes relevant for escape. In addition, while condensation-induced fractionation is the main driver of variations of D/H in water vapour, the differential photolysis of HDO and H2O is a more important factor in determining the isotopic composition of the dissociation products. Three years of observations with the ExoMars TGO Atmospheric Chemistry Suite have clarified the mechanism of atmospheric water loss from Mars, and particularly the fraction of deuterium compared with hydrogen. Analysis of several isotopologues of water in the mid-atmosphere of Mars shows that atomic H and D are produced at perihelion in relative amounts controlled by photolysis. These atoms are able to escape from the atmosphere.

Nitrogen cycling in pastoral livestock systems in Sub-Saharan Africa: knowns and unknowns.

Pastoral systems are the dominant livestock production system in arid and semiarid regions of sub‐Saharan Africa (SSA). They are often the only form of agriculture that can be practiced due to unfavorable climate and soil fertility levels that prevent crop cultivation. Pastoralism can have negative impacts on the environment, including land degradation, greenhouse gas emissions and other gases to the atmosphere, soil erosion, water pollution and biodiversity loss. Here, we review the current knowledge on nitrogen (N) cycling, storage, and loss pathways, with an emphasis on identification of N emission hotspots. Our review reports a large uncertainty in the amount of N lost as ammonia from excreta and manure storage, as well as N losses via nitrate and DON leaching. We also found that another major N loss pathway (18%), soil N2 emissions, has not yet been measured. In order to summarize the available information, we use a virtual pastoral farm, with characteristics and management practices obtained from a real farm, Kapiti Research Station in Kenya. For outlining N flows at this virtual farm, we used published data, data from global studies, satellite imagery and geographic information system (GIS) tools. Our results show that N inputs in pastoral systems are dominated by atmospheric N deposition (˜80%), while inputs due to biological nitrogen fixation seems to play a smaller role. A major N loss pathway is nitrogen leaching (nitrate > DON) from pastures (33%). Cattle enclosures (bomas), where animals are kept during night, represent N emissions hotspots, representing 16% of the total N losses from the system. N losses via ammonia volatilization and N2O were four and three orders of magnitude higher from bomas than from the pasture, respectively. Based on our results, we further identify future research requirements and highlight the urgent need for experimental data collection to quantify nitrogen losses from manure in animal congregation areas. Such information is needed to improve our understanding on N cycling in pastoral systems in semiarid regions and to provide practical recommendations for managers that can help with decision‐making on management strategies in pastoral systems in semiarid savannas.

Nitrogen budgets in Japan from 2000 to 2015: Decreasing trend of nitrogen loss to the environment and the challenge to further reduce nitrogen waste

The benefits of the artificial fixation of reactive nitrogen (Nr, nitrogen [N] compounds other than dinitrogen), in the form of N fertilizers and materials are huge, while at the same time posing substantial threats to human and ecosystem health by the release of Nr to the environment. To achieve sustainable N use, Nr loss to the environment must be reduced. An N-budget approach at the national level would allow us to fully grasp the whole picture of Nr loss to the environment through the quantification of important N flows in the country. In this study, the N budgets in Japan were estimated from 2000 to 2015 using available statistics, datasets, and literature. The net N inflow to Japanese human sectors in 2010 was 6180 Gg N yr−1 in total. With 420 Gg N yr−1 accumulating in human settlements, 5760 Gg N yr−1 was released from the human sector, of which 1960 Gg N yr−1 was lost to the environment as Nr (64% to air and 36% to waters), and the remainder assumed as dinitrogen. Nr loss decreased in both atmospheric emissions and loss to terrestrial water over time. The distinct reduction in the atmospheric emissions of nitrogen oxides from transportation, at −4.3% yr−1, was attributed to both emission controls and a decrease in energy consumption. Reductions in runoff and leaching from land as well as the discharge of treated water were found, at −1.0% yr−1 for both. The aging of Japan's population coincided with the reductions in the per capita supply and consumption of food and energy. Future challenges for Japan lie in further reducing N waste and adapting its N flows in international trade to adopt more sustainable options considering the reduced demand due to the aging population.

Mass–Radius Relationships for Irradiated Ocean Planets

Abstract Massive and water-rich planets should be ubiquitous in the universe. Many of these worlds are expected to be subject to important irradiation from their host star, and display supercritical water layers surrounded by extended steam atmospheres. Irradiated ocean planets with such inflated hydrospheres have been recently shown to be good candidates for matching the mass–radius distribution of sub-Neptunes. Here we describe a model that computes a realistic structure for water-rich planets by combining an interior model with an updated equation of state (EOS) for water, and an atmospheric model that takes into account radiative transfer. We find that the use of inappropriate EOSs can lead to the overestimation of the planetary radius by up to ∼10%, depending on the planet size and composition. Our model has been applied to the GJ 9827 system as a test case and indicates Earth- or Venus-like interiors for planets b and c, respectively. Planet d could be an irradiated ocean planet with a water mass fraction (WMF) of ∼20% ± 10%. We also provide fits for the mass–radius relationships, allowing one to directly retrieve a wide range of planetary compositions, without the requirement to run the model. Our calculations finally suggest that highly irradiated planets lost their H/He content through atmospheric loss processes, and that the leftover material led to either super-Earths or sub-Neptunes, depending on the WMF.

A PSF-based Approach to TESS High quality data Of Stellar clusters (PATHOS) – IV. Candidate exoplanets around stars in open clusters: frequency and age–planetary radius distribution

ABSTRACT The knowledge of the ages of stars hosting exoplanets allows us to obtain an overview on the evolution of exoplanets and understand the mechanisms affecting their life. The measurement of the ages of stars in the Galaxy is usually affected by large uncertainties. An exception are the stellar clusters: For their coeval members, born from the same molecular cloud, ages can be measured with extreme accuracy. In this context, the project PATHOS is providing candidate exoplanets orbiting members of stellar clusters and associations through the analysis of high-precision light curves obtained with cutting-edge tools. In this work, we exploited the data collected during the second year of the Transiting Exoplanet Survey Satellite mission. We extracted, analysed, and modelled the light curves of $\sim 90\, 000$ stars in open clusters located in the Northern ecliptic hemisphere in order to find candidate exoplanets. We measured the frequencies of candidate exoplanets in open clusters for different orbital periods and planetary radii, taking into account the detection efficiency of our pipeline and the false positive probabilities of our candidates. We analysed the age–RP distribution of candidate and confirmed exoplanets with periods <100 d and well constrained ages. While no peculiar trends are observed for Jupiter-size and (super-)Earth-size planets, we found that objects with $4 \lesssim R_{\rm P} \lesssim 13R_{\rm Earth}$ are concentrated at ages ≲200 Myr; different scenarios (atmospheric losses, migration, etc.) are considered to explain the observed age–RP distribution.

Evolution of the Exoplanet Size Distribution: Forming Large Super-Earths Over Billions of Years

Abstract The radius valley, a bifurcation in the size distribution of small, close-in exoplanets, is hypothesized to be a signature of planetary atmospheric loss. Such an evolutionary phenomenon should depend on the age of the star–planet system. In this work, we study the temporal evolution of the radius valley using two independent determinations of host star ages among the California–Kepler Survey (CKS) sample. We find evidence for a wide and nearly empty void of planets in the period–radius diagram at the youngest system ages (≲2–3 Gyr) represented in the CKS sample. We show that the orbital period dependence of the radius valley among the younger CKS planets is consistent with that found among those planets with asteroseismically determined host star radii. Relative to previous studies of preferentially older planets, the radius valley determined among the younger planetary sample is shifted to smaller radii. This result is compatible with an atmospheric loss timescale on the order of gigayears for progenitors of the largest observed super-Earths. In support of this interpretation, we show that the planet sizes that appear to be unrepresented at ages ≲2–3 Gyr are likely to correspond to planets with rocky compositions. Our results suggest that the size distribution of close-in exoplanets and the precise location of the radius valley evolve over gigayears.

Detection of an Atmosphere on a Rocky Exoplanet

Abstract We report the detection of an atmosphere on a rocky exoplanet, GJ 1132 b, which is similar to Earth in terms of size and density. The atmospheric transmission spectrum was detected using Hubble WFC3 measurements and shows spectral signatures of aerosol scattering, HCN, and CH4 in a low mean molecular weight atmosphere. We model the atmospheric loss process and conclude that GJ 1132 b likely lost the original H/He envelope, suggesting that the atmosphere that we detect has been reestablished. We explore the possibility of H2 mantle degassing, previously identified as a possibility for this planet by theoretical studies, and find that outgassing from ultra-reduced magma could produce the observed atmosphere. In this way we use the observed exoplanet transmission spectrum to gain insights into magma composition for a terrestrial planet. The detection of an atmosphere on this rocky planet raises the possibility that the numerous powerfully irradiated super-Earth planets, believed to be the evaporated cores of sub-Neptunes, may, under favorable circumstances, host detectable atmospheres.

The Influence of Age on the Relative Frequency of Super-Earths and Sub-Neptunes

Abstract There is growing evidence that the population of close-in planets discovered by the Kepler mission was sculpted by atmospheric loss, though the typical timescale for this evolution is not well-constrained. Among a highly complete sample of planet hosts of varying ages the age-dependence of the relative fraction of super-Earth and sub-Neptune detections can be used to constrain the rate at which some small planets lose their atmospheres. Using the California-Kepler Survey (CKS) sample, we find evidence that the ratio of super-Earth to sub-Neptune detections rises monotonically from 1 to 10 Gyr. Our results are in good agreement with an independent study focused on stars hotter than the Sun, as well as with forward modeling simulations incorporating the effects of photoevaporation and a CKS-like selection function. We find the observed trend persists even after accounting for the effects of completeness or correlations between age and other fundamental parameters.