Sublimation Of Ice Research Articles

How, when and where current mass flows in Martian gullies are driven by CO2 sublimation

Martian gullies resemble water-carved gullies on Earth, yet their present-day activity cannot be explained by water-driven processes. The sublimation of CO2 has been proposed as an alternative driver for sediment transport, but how this mechanism works remains unknown. Here we combine laboratory experiments of CO2-driven granular flows under Martian atmospheric pressure with 1D climate simulation modelling to unravel how, where, and when CO2 can drive present-day gully activity. Our work shows that sublimation of CO2 ice, under Martian atmospheric conditions can fluidize sediment and creates morphologies similar to those observed on Mars. Furthermore, the modelled climatic and topographic boundary conditions for this process, align with present-day gully activity. These results have implications for the influence of water versus CO2-driven processes in gully formation and for the interpretation of gully landforms on other planets, as their existence is no longer definitive proof for flowing liquids.

Retention of CO ice and gas within 486958 Arrokoth

Kuiper Belt Objects (KBOs) represent some of the most ancient remnants of our solar system, having evaded significant thermal or evolutionary processing. This makes them important targets for exploration as they offer a unique opportunity to scrutinize materials that are remnants of the epoch of planet formation. Moreover, with recent and upcoming observations of KBOs, there is a growing interest in understanding the extent to which these objects can preserve their most primitive, hypervolatile ices. Here, we present a theoretical framework that revisits this issue for small, cold classical KBOs like Arrokoth. Our analytical approach is consistent with prior studies but assumes an extreme cold end-member thermophysical regime for Arrokoth, enabling us to capture the essential physics without computationally expensive simulations. Under reasonable assumptions for interior temperatures, thermal conductivities, and permeabilities, we demonstrate that Arrokoth can retain its original CO stock for Gyrs if it was assembled long after the decay of radionuclides. The sublimation of CO ice generates an effective CO ‘atmosphere’ within Arrokoth’s porous matrix, which remains in near vapor-pressure equilibrium with the ice layer just below, thereby limiting CO loss. According to our findings, Arrokoth expels no more than ≈1022 particles s−1, in agreement with upper limits inferred from New Horizons’ 2019 flyby observations. While our framework challenges recent predictions, it can serve as a benchmark for existing numerical models and be applied to future KBO observations from next-generation telescopes.

JOYS+: Mid-infrared detection of gas-phase SO2 emission in a low-mass protostar

Context. Thanks to the Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST), our ability to observe the star formation process in the infrared has greatly improved. Due to its unprecedented spatial and spectral resolution and sensitivity in the mid-infrared, JWST/MIRI can see through highly extincted protostellar envelopes and probe the warm inner regions. An abundant molecule in these warm inner regions is SO2, which is a common tracer of both outflow and accretion shocks as well as hot core chemistry. Aims. This paper presents the first mid-infrared detection of gaseous SO2 emission in an embedded low-mass protostellar system rich in complex molecules and aims to determine the physical origin of the SO2 emission. Methods. JWST/MIRI observations taken with the Medium Resolution Spectrometer (MRS) of the low-mass protostellar binary NGC 1333 IRAS 2A in the JWST Observations of Young protoStars (JOYS+) program are presented. The observations reveal emission from the SO2 v3 asymmetric stretching mode at 7.35 µm. Using simple slab models and assuming local thermodynamic equilibrium (LTE), we derived the rotational temperature and total number of SO2 molecules. We then compared the results to those derived from high-angular-resolution SO2 data on the same scales (~50–100 au) obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). Results. The SO2 emission from the v3 band is predominantly located on ~50–100 au scales around the mid-infrared continuum peak of the main component of the binary, IRAS 2A1. A rotational temperature of 92 ± 8 K is derived from the v3 lines. This is in good agreement with the rotational temperature derived from pure rotational lines in the vibrational ground state (i.e., v = 0) with ALMA (104 ± 5 K), which are extended over similar scales. However, the emission of the v3 lines in the MIRI-MRS spectrum is not in LTE given that the total number of molecules predicted by a LTE model is found to be a factor of 2 × 104 higher than what is derived for the v = 0 state from the ALMA data. This difference can be explained by a vibrational temperature that is ~100 K higher than the derived rotational temperature of the v = 0 state: Tvib ~ 200 K versus Trot = 104 ± 5 K. The brightness temperature derived from the continuum around the v3 band (~7.35 µm) of SO2 is ~180 K, which confirms that the v3 = 1 level is not collisionally populated but rather infrared-pumped by scattered radiation. This is also consistent with the non-detection of the v2 bending mode at 18–20 µm. The similar rotational temperature derived from the MIRI-MRS and ALMA data implies that they are in fact tracing the same molecular gas. The inferred abundance of SO2 , determined using the LTE fit to the lines of the vibrational ground state in the ALMA data, is 1.0 ± 0.3 × 10−8 with respect to H2, which is on the lower side compared to interstellar and cometary ices (10−8−10−7). Conclusions. Given the rotational temperature, the extent of the emission (~100 au in radius), and the narrow line widths in the ALMA data (~3.5 km s−1), the SO2 in IRAS 2A likely originates from ice sublimation in the central hot core around the protostar rather than from an accretion shock at the disk–envelope boundary. Furthermore, this paper shows the importance of radiative pumping and of combining JWST observations with those from millimeter interferometers such as ALMA to probe the physics on disk scales and to infer molecular abundances.

Enhancing frozen fish quality through polysaccharide-ice glazing: Insights from physical properties and preservation effects

Polysaccharide ice-glazing is a widely employed method for preserving frozen fish, with the choice of polysaccharide playing a crucial role in preservation effectiveness. This research investigates the impact of various polysaccharides, including neutral polysaccharides like konjac glucomannan (KGM) and pullulan (PUL), as well as ionic polysaccharides such as gellan gum (GG), κ-carrageenan (KC), carboxymethyl cellulose (CMC), and xanthan gum (XG), on the physical properties of ice. Additionally, we assess the influence of polysaccharide ice-glazing on the quality of frozen snakehead (Channa argus) fish fillets. Our study shows that the physical properties of polysaccharide-infused ice are affected by both polysaccharide type and concentration. Increasing the polysaccharide concentration led to a reduction in water activity within the supercooled polysaccharide solution. Additionally, the characteristics of ice formed by the polysaccharide solution, including ice crystal size, compressive strength, sublimation rate, and oxygen permeability, consistently decreased. In our comparative analysis, at equivalent polysaccharide concentrations, the PUL solution exhibited the lowest water activity. Notably, PUL-ice demonstrated superior performance, displaying the smallest ice crystal size, highest compressive strength, lowest ice sublimation rate, and the most effective oxygen permeability barrier. Following this in decreasing order of performance were the GG, KC, CMC, XG, and KGM samples. Moreover, when applied to glazing snakehead fish fillets, pullulan ice-glazing outperformed KGM ice-glazing in preserving fish quality, confirming the direct influence of polysaccharide-induced ice properties on fillet preservation outcomes. This study provides essential insights to guide informed decisions in the field of polysaccharide ice-glazing applications, aimed at enhancing the quality of frozen fish.

High-Throughput Quantitative Analysis of Amino Acids in Freeze-Dried Drops Using Time-of-Flight Secondary Ion Mass Spectrometry.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has become a promising analytical tool for molecular profiling in biological applications. However, its ultrahigh vacuum environment and matrix effects hamper the absolute quantitation of solution samples. Herein, we present a rapid high-throughput platform for quantitative ToF-SIMS analysis of amino acids in matrix deposits formed from freeze-dried solution drops through ice sublimation on a parylene film microarray substrate. Droplets of the amino acid solutions, which were mixed with stable isotope-labeled phenylalanine (F*) of high concentration (10 mM), were loaded on wells of the microarray, then frozen and evaporated slowly below the freezing point, forming continuous solid-phase F* matrix deposits. The amino acids (≤500 μM), adequately well dispersed throughout the F* matrix deposits on each well, were quantitatively analyzed by ToF-SIMS in a rapid and high-throughput fashion. The lower limit of quantitation reached below 10 μM.

Dry ice sublimation performance as affected by binding agent, density, and age

AbstractDry ice is one of the world's most in‐demand commodities for cold chain distribution of temperature sensitive products in insulated shippers. A commonly used rule of thumb is that dry ice sublimates about 8% every 24 h, without consideration for dry ice type, size, or geometry. This study explored sublimation rates of dry ice composition (binding agent and density), age, and geometry (size and shape). Dry ice block manufacturing often involves dosing propylene glycol‐water “binder” solution to liquid carbon dioxide. Tests performed in this study revealed that the binding agent did not influence the dry ice sublimation rate. Dry ice density was found to impact sublimation rate. Fresh and aged blocks of similar dimensions and mass were found to have similar performance outcomes. Mass loss curves for pellets and various sized dry ice blocks showed a dependence on surface area and volume. Chunked blocks and pellets with and without binding agent sublimated at similar rates of 2.84 and 2.53% h−1 (w/w), respectively, whereas block varieties with significantly lower surface area to volume ratios had lower sublimation rates of 0.98–1.60% h−1.

Common origin of trapped volatiles in oxidized icy moons and comets

Following spacecraft encounters with comets 67P/C-G and 1P/Halley, it was surprising that O2, expected to be a very minor species in their comas, was observed to outgas at a few percent abundance during their ice sublimation phases. This challenged the direct connection suggested between comets and material in the interstellar medium (ISM), which exhibits a very low O2/H2O gas-phase abundance, leading to a number of papers suggesting novel sources for O2. Since these eccentrically orbiting comets have lost significant amounts of their evaporating surfaces over their lifetimes, the O2 observed must have been stably trapped down to significant depths in these primordial icy bodies. O2 was also seen in the coma by Rosetta, along with other volatiles, long after water ice sublimation began to subside. Here we note that the extensive observations of the icy satellites of Jupiter (Europa, Ganymede, and Callisto) exhibit radiolytic and outgassing processes that provide certain direct parallels to interpretations of recent comet observations. Given that O2 is consistently observed in the atmospheres of icy Jovian satellites, as well as stably trapped as ‘bubbles’ (Johnson and Jesser, 1997) in their water ice surfaces, their spectral observations can help constrain the environment in which Jupiter-family and Oort cloud comets formed given that the observed O2/H2O abundances at both types of comets and icy moons are nearly identical. Based on the approximate charged particle radiation required to produce the observed steady-state concentrations of O2, we suggest that comets likely formed in a far more energetic environment than the ISM. While grains can be irradiated for longer timescales in the neutral ISM, small grains are expected to erode before significant O2 formation and trapping occurs. Independent of celestial dynamics then, an unknown radiation source, may provide insight to the first population of oxidized water ice grains in the early solar system.

Conformer Distributions of n-Propyl Cyanide in the Gas Phase and Following Ice Sublimation Measured by Broadband Rotational Spectroscopy

Conformer Distributions of <i>n</i>-Propyl Cyanide in the Gas Phase and Following Ice Sublimation Measured by Broadband Rotational Spectroscopy

Diurnal Ejection of Boulder Clusters on Comet 67P Lasting beyond 3 au

Ejection of large boulder-like debris is a vigorous form of cometary activity that is unlikely induced by water ice out-gassing alone but rather associated with the sublimation of super-volatile ices. Though perceived on several comets, the actual pattern and mechanism of such activity are still unclear. Here we report on a specialized observation of ejections of decimeter- to meter-sized boulders on comet 67P/Churyumov-Gerasimenko outbound between 2.5 and 3.3 au from the Sun. With a common source region, these events recurred in local morning. The boulders of elongated shapes were ejected in clusters at low inclinations comparable to the solar elevation below 40° at the time. We show that these chunks could be propelled by the surrounding asymmetric gas field that produced a distinct lateral acceleration. Possibly both water and carbon dioxide have contributed to their mobilization, while the season and local topography are among deciding factors. The mechanisms for sustaining regular activity of comets at large heliocentric distances are likely more diverse and intricate than previously thought.

Ejection of porous dust–ice agglomerates from the surface of the cometary nucleus

This paper presents two problems related to the ejection of particles from the surface of the cometary nucleus. The first problem is related to the phase of quiet sublimation. This part of the paper discusses the influence of the water ice sublimation flux on the size of particles that are lifted into the coma. In these considerations, three formulas were used to describe the water ice sublimation flux. The calculations show that the size of the particle lifted into the coma depends on its density and the sublimation flux of water ice. The second mechanism is related to the cometary outburst phase. In this part of the paper, it was proposed that the cometary outburst as a high-energy process may significantly contribute to explaining the presence of small particles in the coma. Based on the calculations performed, it was shown that the dimensions of these particles depend on the adopted value of the power index in the power law. Based on the considerations presented in this paper, the presence of both large and fine dust particles observed in the coma during the Rosetta mission can be explained.

Properties of the gas escaping from a non-isothermal porous dust surface layer of a comet

ABSTRACT Estimation of the properties of the sublimation products leaving the cometary nucleus is one of the significant questions in the study of the dusty-gas flow following the Rosetta mission. It is widely assumed that the temperature of the water molecules emitted is the temperature of ice directly exposed to the surface. However, it is the simplest non-verified idealization if the refractory porous material lays on the surface and controls the energy driving the ice sublimation. This highly non-isothermal surface layer should change the vapour temperature as the molecules pass through it from the icy region to the vacuum. A key sustaining observation here comes from the MIRO experiment on Rosetta which measured the velocity of water vapour. The observed gas velocities are visibly higher than can be explained by emission at typical ice surface temperature. To investigate the issue, we simulate a gas flow through a non-isothermal porous dust layer and analyse the temperature of molecules emitted. Monodisperse and bimodal layers, as well as layers made of porous aggregates, are considered. Modelling is carried out for various porosity values, different particle sizes, and dust layer thicknesses. The simulation results are embedded in two-layer thermal models including the effective thermal conductivity, volumetric light absorption, and the resistance of the dust layer to the gas flow.

Surviving the heat: multiwavelength analysis of V883 Ori reveals that dust aggregates survive the sublimation of their ice mantles

ABSTRACT Investigating the response of icy dust aggregates to water ice sublimation is essential for understanding the formation and properties of planetesimals in protoplanetary discs. However, their fate remains unclear, as previous studies suggest that aggregates could either survive or completely fall apart to (sub)μm-sized grains. Protoplanetary discs around stars undergoing accretion outbursts represent a unique laboratory to study the ice sublimation process, as the water snowline is pushed outward to regions accessible to current observatories. In this work, we aim to understand the aggregates’ response to ice sublimation by focusing on V883 Ori, a system currently undergoing a powerful accretion outburst. We present new analysis of archival high-resolution ALMA observations of the protoplanetary disc of V883 Ori at 0.88, 1.3, 2.0, and 3.1 mm, and derive new radial spectral index profiles, which we compare with predictions from one-dimensional dust evolution simulations. In the region of V883 Ori where water ice has sublimated, we find lower spectral indices than previously obtained, indicating the presence of cm-sized particles. Coupled with our dust evolution models, we find that the only way to explain their presence is to assume that they formed before the outburst and survived the sublimation process. The resilience of dust aggregates to such intense events leads us to speculate that it may extend to other environments with more gentle heating, such as pebbles drifting through the water snowline in quiescent protoplanetary discs. In that case, it may alter the formation pathway of dry planetesimals interior to the snowline.

Thermophysical properties of lunar regolith simulant LHS-1 and ice sublimation kinetics in its mixtures with frozen water

A recently developed lunar regolith simulant LHS-1 is used currently to advance the technologies for water extraction from icy regolith in the polar regions of the Moon. However, thermophysical properties of LHS-1 at low temperatures have not been studied yet, which hinders the development of these technologies. It is also unclear whether experimental data on the rate of ice sublimation in LHS-1/ice mixtures can be applied to the actual icy regolith of the Moon. In the present paper, the specific heats and thermal diffusivities of LHS-1 and its finer version LHS-1D were studied at low temperatures using differential scanning calorimetry and laser flash analysis. The thermal diffusivities of LHS-1 and LHS-1D have been measured in the temperature range of 148−300 K in a helium environment at pressures of about 90 kPa and less than 1 Pa. The reduced pressure decreased the thermal diffusivity by several times owing to the decreased role of helium in the heat transfer during the test. The thermal diffusivity also decreased with increasing temperature and decreasing particle size. The specific heats of dry simulants have been measured in the temperature range of 110−320 K. The obtained values are close to the specific heats of the Apollo regolith samples at the same temperatures. The specific heats of LHS-1 and LHS-1D, mixed with water, have been measured in the temperature range of 110−340 K. The theoretically expected increase in specific heat due to the addition of 3 − 5 wt % ice was within the experimental error. The ice sublimation rates in LHS-1/ice and LHS-1D/ice mixtures have been measured at temperatures of 240, 247, and 258 K at pressure of 4 Pa. The sublimation rate decreases with time for all samples, which may be associated with increasing vapor pressure over the subliming surface as the sublimation front propagates downward. The analysis of the obtained data has shown that the area of the subliming surface is much less than the surface area of the simulant particles. This should be taken into account when the results of experiments with simulant/ice mixtures are applied to the actual icy regolith on the Moon.

UV-photoprocessing of acetic acid (CH3COOH)-bearing interstellar ice analogues

ABSTRACT Acetic acid (CH3COOH) was detected in the gas towards interstellar clouds, hot cores, protostars, and comets. Its formation in ice mantles was proposed, and acetic acid awaits detection in the infrared spectra of the ice as most of the other complex organic molecules except methanol. The thermal annealing and UV-irradiation of acetic acid in the ice was simulated experimentally in this work under astrophysically relevant conditions. The experiments were performed under ultrahigh vacuum conditions. An ice layer was formed by vapour deposition onto a cold substrate, and was warmed up or exposed to ultraviolet (UV) photons. The ice was monitored by infrared spectroscopy, while the molecules desorbing to the gas phase were measured using a quadrupole mass spectrometer. The transformation of the CH3COOH monomers to cyclic dimers occurs at 120 K, and the crystal form composed of chain polymers was observed above 160 K during warm-up of the ice. Ice sublimation proceeds at 189 K in our experiments. Upon UV-irradiation, simpler species and radicals are formed, which leads to a residue made of complex molecules after warm-up to the room temperature. The possible formation of oxalic acid needs to be confirmed. The photodestruction of acetic acid molecules is reduced when mixed with water in the ice. This work may serve to search for the acetic acid photoproducts in lines of sight where this species is detected. A comparison of the reported laboratory infrared spectra with current JWST observations allows to detect or set upper limits on the CH3COOH abundances in interstellar and circumstellar ice mantles.

NEMLİ VE ZORLANMIŞ TAŞINIMLI KAPALI HACİMLERDE YARIKÜRESEL BUZ SÜBLİMASYONUNUN ANALİTİK İNCELENMESİ

In real life, sublimation of ice under certain conditions results in non-uniform formation of ice cubes with irregular shapes. During extracting these irregularly shaped cubes from enclosed spaces, the openings through which the cubes move can be plugged. A deep analysis of the sublimation process should be applied to make the shape of the ice cubes homogeneous and smooth-edged. Although there is an analytical method for the sublimation of spherical ice in literature, the hemispherical shape has not been studied. Furthermore, if ice formation and sublimation occur simultaneously within a place confined by a wall, novel approaches are necessary. In the current study, an analytical method has been proposed for the sublimation from a hemispherical ice sample as a combination of the models for the spherical and circular flat surfaces. The sublimation rate calculated by this new analytical method has been compared to the results from the weighing experiments and visualizations where the sublimation over time was measured by processing a series of images of ice cubes. There is a good agreement between the calculated values and the mass loss observed in the visualized images and the weighted samples. Thus, it is concluded that the sublimation rate is correlated with the velocity, temperature, and relative humidity of the air flowing over the ice cubes undergoing sublimation.

Comets, sliding of surface dust on illuminated surfaces

In our paper we presented the results of our laboratory experiments dealing with the formation and sliding of the desiccated nonvolatile granular material down the samples of potential cometary analogs. The studied samples were composed of porous aggregates containing water ice, quartz sand and charcoal. Their surfaces were initially free of desiccated material. We have found, that under special conditions the sand released due to the sublimation of ice may almost continuously slide down the surface and leave it almost free of sand. The results of the experiments were compared to the observations of scarps on the nucleus of comet 67P/Churyumov–Gerasimenko.

JWST Reveals Excess Cool Water near the Snow Line in Compact Disks, Consistent with Pebble Drift

Previous analyses of mid-infrared water spectra from young protoplanetary disks observed with the Spitzer-IRS found an anticorrelation between water luminosity and the millimeter dust disk radius observed with ALMA. This trend was suggested to be evidence for a fundamental process of inner disk water enrichment proposed decades ago to explain some properties of the solar system, in which icy pebbles drift inward from the outer disk and sublimate after crossing the snow line. Previous analyses of IRS water spectra, however, were uncertain due to the low spectral resolution that blended lines together. We present new JWST-MIRI spectra of four disks, two compact and two large with multiple radial gaps, selected to test the scenario that water vapor inside the snow line is regulated by pebble drift. The higher spectral resolving power of MIRI-MRS now yields water spectra that separate individual lines, tracing upper level energies from 900 to 10,000 K. These spectra clearly reveal excess emission in the low-energy lines in compact disks compared to large disks, demonstrating an enhanced cool component with T ≈ 170–400 K and equivalent emitting radius R eq ≈ 1–10 au. We interpret the cool water emission as ice sublimation and vapor diffusion near the snow line, suggesting that there is indeed a higher inward mass flux of icy pebbles in compact disks. Observation of this process opens up multiple exciting prospects to study planet formation chemistry in inner disks with JWST.

Recurring Activity Discovered on Quasi-Hilda 2009 DQ118

We have discovered two epochs of activity on quasi-Hilda 2009 DQ118. Small bodies that display comet-like activity, such as active asteroids and active quasi-Hildas, are important for understanding the distribution of water and other volatiles throughout the solar system. Through our NASA Partner Citizen Science project, Active Asteroids, volunteers classified archival images of 2009 DQ118 as displaying comet-like activity. By performing an in-depth archival image search, we found over 20 images from UT 2016 March 8–9 with clear signs of a comet-like tail. We then carried out follow-up observations of 2009 DQ118 using the 3.5 m Astrophysical Research Consortium Telescope at Apache Point Observatory, Sunspot, New Mexico, USA and the 6.5 m Magellan Baade Telescope at Las Campanas Observatory, Chile. These images revealed a second epoch of activity associated with the UT 2023 April 22 perihelion passage of 2009 DQ118. We performed photometric analysis of the tail and find that it had a similar apparent length and surface brightness during both epochs. We also explored the orbital history and future of 2009 DQ118 through dynamical simulations. These simulations show that 2009 DQ118 is currently a quasi-Hilda and that it frequently experiences close encounters with Jupiter. We find that 2009 DQ118 is currently on the boundary between asteroidal and cometary orbits. Additionally, it has likely been a Jupiter family comet or Centaur for much of the past 10 kyr and will be in these same regions for the majority of the next 10 kyr. Since both detected epochs of activity occurred near perihelion, the observed activity is consistent with sublimation of volatile ices. 2009 DQ118 is currently observable until ∼mid-October 2023. Further observations would help to characterize the observed activity.

Cliff collapse on Comet 67P/Churyumov–Gerasimenko – I. Aswan

ABSTRACT The Aswan cliff on Comet 67P/Churyumov–Gerasimenko collapsed on 2015 July 10. Thereby, relatively pristine comet material from a depth of $\sim 12\, \mathrm{m}$ was exposed at the surface. Observations of the collapse site by the microwave instrument Rosetta/Microwave Instrument for Rosetta Orbiter (MIRO) have been retrieved from 8 months prior to collapse, as well as from 5, 7, and 11 months post-collapse. The MIRO data are analysed with thermophysical and radiative transfer models. The pre-collapse observations are consistent with a 30 MKS thermal inertia dust mantle with a thickness of at least $3\, \mathrm{cm}$. The post-collapse data are consistent with (1) a dust/water–ice mass ratio of 0.9 ± 0.5 and a molar CO2 abundance of ∼30 per cent relative to water; (2) formation of a dust mantle after ∼7 months, having a thickness of a few millimetres or a fraction thereof; (3) a CO2 ice sublimation front at 0.4 cm that withdrew to 2.0 cm and later to $20\pm 6\, \mathrm{cm}$; (4) a thermal inertia ranging 10–45 MKS; (5) a gas diffusivity that decreased from $0.1$ to $0.001\, \mathrm{m^2\, s^{-1}}$; and (6) presence of a solid-state greenhouse effect parts of the time. The data and the analysis provide a first empirical glimpse of how ice-rich cometary material ages and evolves when exposed to solar heating.

Calorimetry

Three “coffee-cup” calorimetry experiments: 1) Use of the Law of Dulong and Petit to identify an unknown metal 2) Measurement of the enthalpy of sublimation of dry ice 3) Exploration of the relationship between surface area and the rate of heat transfer and the amount of heat transferred Featuring contributions from Tamara Fitzjarrald