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Anil Bhardwaj

Physical Research Laboratory, Ahmedabad, Director

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Anil Bhardwaj is the Director of Physical Reserach Laboratory, Ahmedabad, India. He is the recipient of the SS Bhatnagar Award in 2007. He was NRC Senior Research Associate at NASA MSFC during 2004-2005. He is a Fellow of Indian Academy of Sciences, INSA, NASI, IGU, and KASc. He is the Member of International Academy of Astronautics. He is Vice-Chair of COSPAR Commission B, member of IAU, and INSA-ICSU Committee.He received the Infosys Prize in Physical Sciences in 2016. http://www.infosys-science-foundation.com/prize/laureates/2016/anil-bhardwaj.asp
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Papers by Anil Bhardwaj

Contextual characterization study of Chandrayaan-3 primary landing site

Monthly Notice of Royal Astronomical Society, 2023

Chandrayaan-3 is an upcoming lunar mission of India aimed at soft landing and carrying out first-... more Chandrayaan-3 is an upcoming lunar mission of India aimed at soft landing and carrying out first-ever in situ investigations at a high-latitude location on the Moon. Chandrayaan-3 consists of a propulsion module, a lander and a rover, that carry a set of payloads for conducting in situ science experiments. In this work, contextual characterization of the primary landing site (PLS) located at 69.367621 ˚S, 32.348126 ˚E is carried out in terms of identification, geomorphology, composition, and thermophysical context using the best-ever high-resolution data sets. Our geomorphological study indicates that the PLS is safe for landing with slope less than 4 ˚in about 78 per cent of landing area and an average elevation variation of about 169 m. The spectral analysis suggests that the region must have experienced extensive space weathering. Compositional analysis indicates that the landing region has a typical highland type of soil characteristics with Mg (4.3–5.2 wt. per cent), Fe (4.2–4.9 wt. per cent), Ca (10–11 wt. per cent), and Ti (0.25–0.35 wt. per cent). Thermophysical analyses show ∼30 and 175 K variability in spatial and diurnal temperatures at the PLS – an indicative of a local terrain of distinctive thermophysical characteristics. With important science instruments onboard, Chandrayaan-3 will provide a unique opportunity towards looking at localized variations leading to an improved understanding of the lunar surface.

Amorphous 1-propanol interstellar ice beyond its melting point

Monthly Notice of Royal Astronomical Society, 2024

The recent discovery of 1-propanol (CH3CH2CH2OH) in the interstellar medium (ISM) is of tremendou... more The recent discovery of 1-propanol (CH3CH2CH2OH) in the interstellar medium (ISM) is of tremendous interest since fatty alcohols have been proposed as constituents of proto-cell membranes. Motivated by this discovery, we present the laboratory mid- infrared (MIR) and vacuum ultraviolet (VUV) absorption spectra of 1-propanol ice under astrochemical conditions, mimicking an icy mantle on cold dust in the ISM. Both MIR and VUV spectra were recorded at ultrahigh vacuum of ∼10^-9 mbar and at temperatures ranging from 10 K to sublimation. The morphology of the 1-propanol ice deposited at 10 K was amorphous. By warming the ice to temperatures of 140 K and above, with subsequent recording of IR spectra, we observe complete sublimation of 1-propanol molecules from the substrate around 170 K. No amorphous-to-crystalline phase change was observed upon warming to higher temperatures. Additionally, we observe the IR and VUV signatures of 1-propanol ice on the substrate well beyond its melting point (147 K). To the best of our knowledge, this is the first reported observation of a molecular ice staying well beyond its melting point under such conditions. This result shows that the morphology of icy mantles on ISM cold dust grains is more complex than previously thought. Our atomistic molecular dynamics simulations capture the experimental trends and shed light on the microscopic origin of this unusual phase behaviour of 1-propanol.

Meteorite fall in Bhojade village, Kopargaon taluk, Ahmednagar district, Maharashtra, India

CURRENT SCIENCE, VOL. 124, NO. 10, 25 MAY 2023 1139, 2023

Ultraviolet spectrum reveals the presence of ozone on Jupiter's moon Callisto

Icarus, 2024

Sulphur dioxide (SO 2) is known to be present on Callisto. In this paper, we studied the chemical... more Sulphur dioxide (SO 2) is known to be present on Callisto. In this paper, we studied the chemical evolution of SO 2 astrochemical ice induced by irradiation using 9 eV (137.7 nm) vacuum ultraviolet light produced from the highflux beamline of the storage ring at the National Synchrotron Radiation Research Centre in Taiwan. Ultraviolet absorption spectra of the irradiated ice recorded in the 240-320 nm region reveal a broad absorption band indicating the formation of ozone. By comparing these laboratory spectra with Hubble Space Telescope data of the surface of Callisto in this spectral region, we find compelling evidence to consider the presence of ozone on Callisto. Furthermore, there is an additional band peaking at 309 nm whose assignment is as yet unclear but is quite similar to a band observed on Ganymede, thus leading us to suspect a common molecular source.

Optical spectroscopy of comets using Hanle Echelle Spectrograph (HESP)

MNRAS, 2024

Observing the vibrational/rotational lines in a comet’s optical spectrum requires high-resolution... more Observing the vibrational/rotational lines in a comet’s optical spectrum requires high-resolution spectroscopy, as they are otherwise seen as a blended feature. To achieve this, we have obtained medium and high-resolution (R ( λ/ dλ) = 30 000 and 60 000) spectra of several comets, including C/2015 V2 (Johnson), 46P/Wirtanen, 41P/Tuttle–Giacobini–Kres ´ak, and 38P/Stephan–Oterma, using the Hanle Echelle Spectrograph (HESP) mounted on the 2-m Himalayan Chandra Telescope (HCT) in India. The spectra effectively cover the wavelength range 3700–10 000 Å, allowing us to probe the various vibrational bands and band sequences to identify the rotational lines in the cometary molecular emission. We were also able to separate the cometary Oxygen lines from the telluric lines and analyse the green-to-red (G/R) forbidden oxygen [O I ] ratios in a few comets. For comets C/2015 V2, 46P, and 41P, the computed G/R ratios, 0.04 ±0.01, 0.04 ±0.01, and 0.08 ±0.02, respectively, point to H 2 O being a major source of Oxygen emissions. Notably, in the second fibre pointing at a location 1000 km away from the photocentre of comet 46P, the G/R ratio reduced by more than half the value observed in the first fibre, indicating the effects of quenching within the inner coma. We also measured the NH 2 ortho-to-para ratio of comet 46P to be about 3.41 ±0.05 and derived an ammonia ratio of 1.21 ±0.03 corresponding to a spin temperature of ∼26 K. With these, we present the results of the study of four comets from different cometary reservoirs using medium and high-resolution optical spectroscopy, emphasizing the capabilities of the instrument for future cometary studies.

Chandrayaan-3 APXS elemental abundance measurements at lunar high latitude

Nature, 2024

The elemental composition of the lunar surface provides insights into mechanisms of the formation... more The elemental composition of the lunar surface provides insights into mechanisms of the formation and evolution of the Moon. The chemical composition of lunar regolith have so far been precisely measured using the samples collected by the Apollo, Luna and Chang’e 5 missions, which are from equatorial to mid-latitude regions; lunar meteorites, whose location of origin on the Moon is unknown5,6; and the in situ measurement from the Chang’e 3 and Chang’e 4 missions, which are from the mid-latitude regions of the Moon. Here we report the first in situ measurements of the elemental abundances in the lunar southern high-latitude regions by the Alpha Particle X-ray Spectrometer (APXS) experiment10 aboard the Pragyan rover of India’s Chandrayaan-3 mission. The 23 measurements in the vicinity of the Chandrayaan-3 landing site show that the local lunar terrain in this region is fairly uniform and primarily composed of ferroan anorthosite (FAN), a product of the lunar magma ocean (LMO) crystallization. However, observation of relatively higher magnesium abundance with respect to calcium in APXS measurements suggests the mixing of further mafic material. The compositional uniformity over a few tens of metres around the Chandrayaan-3 landing site provides an excellent ground truth for remote-sensing observations.

Observations of the Quiet Sun during the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM: Elemental Abundances in the Quiescent Corona

The Astrophysical Journal Letters, 2021

Elements with low first ionization potential (FIP) are known to be 3-4 times more abundant in act... more Elements with low first ionization potential (FIP) are known to be 3-4 times more abundant in active region loops of the solar corona than in the photosphere. There have been observations suggesting that this observed "FIP bias" may be different in other parts of the solar corona and such observations are thus important in understanding the underlying mechanism. The Solar X-ray Monitor (XSM) on board the Chandrayaan-2 mission carried out spectroscopic observations of the Sun in soft X-rays during the 2019-2020 solar minimum, considered to be the quietest solar minimum of the past century. These observations provided a unique opportunity to study soft X-ray spectra of the quiescent solar corona in the absence of any active regions. By modeling high-resolution broadband X-ray spectra from XSM, we estimate the temperature and emission measure during periods of possibly the lowest solar X-ray intensity. We find that the derived parameters remain nearly constant over time with a temperature around 2 MK, suggesting the emission is dominated by X-ray bright points. We also obtain the abundances of Mg, Al, and Si relative to H, and find that the FIP bias is ∼2, lower than the values observed in active regions.

Multiwavelength Observations of a B-class Flare Using XSM, AIA, and XRT

We present multiwavelength observations by Chandrayaan-2/Solar X-ray Monitor, Solar Dynamics Obse... more We present multiwavelength observations by Chandrayaan-2/Solar X-ray Monitor, Solar Dynamics Observatory/ Atmospheric Imaging Assembly, and Hinode/X-Ray Telescope (XRT) of a B-class flare observed on 2021 February 25, originating from an active region (AR 12804) near the northwest limb. The microflare lasts for ∼30 minutes and is composed of hot loops reaching temperatures of 10 MK. We report excellent agreement (within 20%) for the average effective temperatures obtained at the flare peak from all the three instruments, which have different temperature sensitivities. The XRT filter combination of Be-thin and Be-med provides an excellent opportunity to measure the high temperatures in such microflare events. The elemental abundances during the evolution of the microflare are also studied and observed to drop toward photospheric values at the flare peak time, compared to coronal values during the rise and decay phase. This is consistent with previous XSM studies.

Extraterrestrial Impacts Creating Architectures for Life

J Indian Inst Sci, 2023

Prebiotic chemical evolution that led to the emergence of life on primitive Earth is interlinked ... more Prebiotic chemical evolution that led to the emergence of life on primitive Earth is interlinked with the delivery of organic material through the impact of comets, asteroids and meteorites. The catastrophic nature of impact leads to significant damage to planetary bodies. The high pressure and temperature can cause molecules to break apart and they may not survive in such extreme conditions. Also, impact-induced shock can cause impacted molecules to undergo vibration, dissociation, deformation, depending on their chemical properties and thus can offer enormous potential for the synthesis of building blocks of life. Novel experimental and theoretical approaches are required to simulate the phenomena that occur during impacts. In this brief review, we discuss impacts and related processes through laboratory experiments and simulations that study the impact-shock chemistry and its role in the Origins of Life.

X-rays in the Solar System

This chapter was originally published in the book Encyclopedia of Solar system. The copy attached... more This chapter was originally published in the book Encyclopedia of Solar system. The copy attached is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non-commercial research, and educational use. This includes without limitation use in instruction at your institution, distribution to specific colleagues, and providing a copy to your institution's administrator. All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution's website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's

Boulder Fall Ejecta: Present Day Activity on Mars

Geophysical Research Letters, 49, e2021GL096808, 2022

Boulder falls are an archives of recent surface activity on Mars, however, determining how recent... more Boulder falls are an archives of recent surface activity on Mars, however, determining how recently they fell remains elusive. Our multitemporal HiRISE image analysis shows that new tracks are characterized by a herringbone-like ejecta pattern at each boulder bounce that we call boulder fall ejecta (BFE). First systematic survey of BFE revealed ∼4,500 tracks whose total integrated track length is ∼900 km. Our BFE longevity analysis reveals that these tracks likely formed in the last few decades. From few examples we also observed slope streaks originating from BFE tracks, providing additional evidence favoring a dry origin theory. BFE fade in as little as ∼2 to 4 Mars years, whereas, others can persist >6 Mars years suggesting differential weathering. Nearly 30% of BFE are observed in the Cerberus Fossae region, which suggests it is one of the most seismically active regions. Thus, BFE can be used to recognize very recent surface processes on planetary surfaces.

Meteorite fall in Bhojade village, Kopargaon taluk, Ahmednagar district, Maharashtra, India

by Anil Bhardwaj and Dwijesh Ray

CURRENT SCIENCE, VOL. 124, NO. 10, 25 MAY 2023, 2023

The Diyodar meteorite fall in India

CURRENT SCIENCE, 152 VOL. 124, NO. 2, 25 JANUARY 2023, 2023

A study on the solar coronal dynamics during the post-maxima phase of the solar cycle 24 using S -band radio signals from the Indian Mars Orbiter Mission

by Anil Bhardwaj, Raj Choudhary, and Richa Naja Jain

Monthly Notices of the Royal Astronomical Society , 2022

Radio signals from India's Mars Orbiter Mission (MOM) have been used to study turbulence in the s... more Radio signals from India's Mars Orbiter Mission (MOM) have been used to study turbulence in the solar plasma during the post-maximum phase of solar cycle 24. S-band (2.29 GHz) radio carrier downlink signals from MOM were received at the Indian Deep Space Network, Bangalore, and frequency residuals were spectrally analysed to obtain coronal turbulence spectra at heliocentric distances ranging between 4 and 20 R , corresponding to coronal regions where the solar wind is primarily accelerated. The frequency fluctuation spectrum relates to the turbulence regime in the near-Sun region. The turbulence power spectrum (the temporal spectrum of frequency fluctuations) at smaller heliocentric distances (< 10 R) reveals flattening in lower-frequenc y re gions, with a spectral inde x α f ∼ 0.3 −0.5, which corresponds to the solar wind acceleration re gion. F or larger heliocentric distances (> 10 R), the curve steepens with a spectral index α f ∼ 0.7 −0.8, a value close to 2/3 and indicative of a developed Kolmogorov-type turbulence spectrum. The findings are consistent with earlier results. Plausible explanations to support the theory of coronal heating by magnetohydrodynamic waves and the acceleration of the solar wind are presented. An insight into the feeble maximum of solar cycle 24 is discussed.

New Signatures of Bio-Molecular Complexity in the Hypervelocity Impact Ejecta of Icy Moon Analogues

Life 2022, 12, 508, 2022

Impact delivery of prebiotic compounds to the early Earth from an impacting comet is considered t... more Impact delivery of prebiotic compounds to the early Earth from an impacting comet is considered to be one of the possible ways by which prebiotic molecules arrived on the Earth. Given the ubiquity of impact features observed on all planetary bodies, bolide impacts may be a common source of organics on other planetary bodies both in our own and other solar systems. Biomolecules such as amino acids have been detected on comets and are known to be synthesized due to impact induced shock processing. Here we report the results of a set of hypervelocity impact experiments where we shocked icy mixtures of amino acids mimicking the icy surface of planetary bodies with high-speed projectiles using a two-stage light gas gun and analyzed the ejecta material after impact. Electron microscopic observations of the ejecta have shown the presence of macroscale structures with long polypeptide chains revealed from LCMS analysis. These results suggest a pathway in which impact on cometary ices containing building blocks of life can lead to the synthesis of material architectures that could have played a role in the emergence of life on the Earth and which may be applied to other planetary bodies as well.

Processes governing the VIS/NIR spectral reflectance behavior of lunar swirls

Astronomy and Astrophysics, 639, A12, pp.1-18 , 2020

We investigated six bright swirls associated with magnetic anomalies of variable strength using C... more We investigated six bright swirls associated with magnetic anomalies of variable strength using Chandrayaan-1 Moon Mineralogy Mapper (M 3) hyperspectral image data. We examined the 3 µm absorption band generally ascribed to solar wind-induced OH/H 2 O and spectral trends in the near-infrared wavelength range at on-swirl and off-swirl locations. We found that the 3 µm absorption band is weaker at on-swirl than at off-swirl locations and shows only weak variations with time-of-day. This result is consistent with magnetic anomaly shielding that reduces solar wind interaction with the surface. For a small swirl structure in Mare Moscoviense, we found the 3 µm absorption band to be similar to that of its surroundings due to the absence of strong magnetic shielding. Our spectral analysis results at on-swirl and off-swirl locations suggest that the spectral trends at on-swirl and off-swirl locations cannot always be explained by reduced space-weathering alone. We propose that a combination of soil compaction possibly resulting from the interaction between the surface and cometary gas and subsequent magnetic shielding is able to explain all observed on-swirl vs. off-swirl spectral trends including the absorption band depth near 3 µm. Our results suggest that an external mechanism of interaction between a comet and the uppermost regolith layer might play a significant role in lunar swirl formation.

A photochemical model of ultraviolet atomic line emissions in the inner coma of comet 67P/Churyumov-Gerasimenko

Icarus, 2020

Alice ultraviolet spectrometer onboard Rosetta space mission observed several spectroscopic emiss... more Alice ultraviolet spectrometer onboard Rosetta space mission observed several spectroscopic emissions emanated from volatile species of comet 67P/Churyumov-Gerasimenko (hearafter 67P/C-G) during its entire escorting phase. The measured emission intensities, when the comet was at around 3 AU pre-perihelion, have been used to derive electron densities in the cometary coma assuming that H I and O I lines are solely produced by electron impact dissociative excitation of cometary parent species (Feldman et al., 2015). We have developed a photochemical model for comet 67P/C-G to study the atomic hydrogen (H I 1216, 1025, & 973 Å), oxygen (O I 1152, 1304, & 1356 Å), and carbon (C I 1561 & 1657 Å) line emissions by accounting for major production pathways. The developed model has been used to calculate the emission intensities of these lines as a function of nucleocentric projected distance and also along the nadir view by varying the input parameters, viz., neutral abundances and cross sections. We have quantified the percentage contributions of photon and electron impact dissociative excitation processes to the total intensity of the emission lines, which has an important relevance for the analysis of Alice observed spectra. It is found that in comet 67P/C-G, with a neutral gas production rate of about 10 27 s −1 when it was at 1.56 AU from the Sun, photodissociative excitation processes are more significant compared to electron impact reactions in determining the atomic emission intensities. Based on our model calculations, we suggest that the observed atomic hydrogen, oxygen, and carbon emission intensities can be used to derive H 2 O, O 2 , and CO, abundances, respectively, rather than electron density in the coma of 67P/C-G, when the comet has a gas production rate of 10 27 s −1 or more.

Ground calibration of Alpha Particle X-ray Spectrometer (APXS) on-board Chandrayaan-2 Pragyaan rover: An empirical approach

by Anil Bhardwaj and Swaroop Banerjee

Planetary and Space Science 187, 104923, 2020

Alpha Particle X-ray Spectrometer (APXS) was one of the scientific experiments on-board the Pragy... more Alpha Particle X-ray Spectrometer (APXS) was one of the scientific experiments on-board the Pragyaan rover of the Chandrayaan-2 mission to Moon, with the objective to determine the elemental composition of the lunar surface near the landing site in the south polar region of the Moon. APXS estimates the abundances by measuring the characteristic X-ray lines of the constituent elements present in the target surface, when irradiated by the onboard Cm-244 radioactive source. X-ray spectral measurement in the energy range of 0.8-25 keV with an energy resolution of e135 eV at 5.89 keV enables APXS to detect all the major rock-forming elements, such as Na, Mg, Al, Si, Ca, Ti, and Fe. This paper describes the calibration of APXS as an X-ray spectrometer, provides a procedure for quantitative estimation of elemental concentrations based on the measurements of standard geochemical reference materials and provides the detection limits of the major elements. It is shown that, following this procedure, the concentration of the major elements in any sample can be determined with typical accuracy of better than 10% of the actual value.

Lunar regolith and water ice escape due to micrometeorite bombardment

Icraus, 2020

Dust particles exist everywhere in interplanetary space and they evolve dynamically after their o... more Dust particles exist everywhere in interplanetary space and they evolve dynamically after their origination from the sources like Asteroid belt, Kuiper belt, comets or space debris left during the formation of solar system. These micrometeorites encounter the inner planets, while they spiral-in towards the Sun. From whichever come to Earth, many particles are ablated in the Earth's atmosphere and leave the metallic ions behind. In case of Moon, all such particles can reach the surface without ablation owing to the absence of atmosphere. Due to the impact of hypervelocity dust particles on lunar surface, ejecta come out in the lunar environment. In some cases, the ejecta velocity could be larger than the escape velocity and particles may be able to escape from Moon. Further, the escaping ejecta may carry water ice (volatiles), whenever incoming projectiles hit the surface in polar region with the water ice present. In this paper, we have computed the ejecta parameters and estimated the possible escape of volatiles from Moon, using Galileo observations of the dust particles near Moon. Considering the incident angle distribution, the upper limit of regolith escape rate is found to be ~2.218 � 10 4 [1.662 � 10 4 , 10.232 � 10 4 ] kg/s. Similarly, the upper limit of water ice escape rate is found to be ~1.988 � 10 7 [1.562 � 10 7 , 7.567 � 10 7 ] kg/s. On one side, Moon is found to be gradually becoming heavier due to its one order higher incoming dust particles than those escaping from it. While on the other side, Moon could be depleted of water ice (volatiles) resources over a period of time, because of the escape due to micrometeorite impact. The results presented here could be useful to understand the dust and volatile escape from Moon.

The dayside ionosphere of Mars: Comparing a one-dimensional photochemical model with MAVEN Deep Dip campaign observations

Icarus, 337, 113502, 2020

A one dimensional photochemical model for the dayside ionosphere of Mars has been developed for c... more A one dimensional photochemical model for the dayside ionosphere of Mars has been developed for calculating the density profiles of ions and electrons under steady state photochemical equilibrium condition. The study focuses on the Deep Dip campaigns of the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) and used the in-situ measurements of neutral density profiles, solar flux and electron temperatures from instruments onboard MAVEN as input to the model. An energy deposition model is employed for calculating the attenuated photon flux and photoelectron flux at different altitudes in the ionosphere. The Analytical Yield Spectrum approach is used for calculating the photoelectron fluxes. Volume production rates of major primary ions, CO + 2 , CO + , O + , C + , N + 2 , and N + , due to photon and photoelectron impact are calculated and used as input to the model in which ion-neutral chemistry in the dayside ionosphere is simulated. The modeled ion profiles are compared with the ion mode observations of Neutral Gas Ion Mass Spectrometer (NGIMS) and electron density estimates from Langmuir Probe and Waves (LPW). The model could reproduce the observed structure of the major ion profiles O + 2 , CO + 2 , and electron density reasonably well. However, when the magnitudes are compared, the modeled values are roughly a factor of 2 larger than observation. By reducing the neutral CO 2 density, the model outputs and the observed ion profiles and electron density profile can become closer. The model also calculated the densities of 11 other ions, viz.

Contextual characterization study of Chandrayaan-3 primary landing site

Monthly Notice of Royal Astronomical Society, 2023

Chandrayaan-3 is an upcoming lunar mission of India aimed at soft landing and carrying out first-... more Chandrayaan-3 is an upcoming lunar mission of India aimed at soft landing and carrying out first-ever in situ investigations at a high-latitude location on the Moon. Chandrayaan-3 consists of a propulsion module, a lander and a rover, that carry a set of payloads for conducting in situ science experiments. In this work, contextual characterization of the primary landing site (PLS) located at 69.367621 ˚S, 32.348126 ˚E is carried out in terms of identification, geomorphology, composition, and thermophysical context using the best-ever high-resolution data sets. Our geomorphological study indicates that the PLS is safe for landing with slope less than 4 ˚in about 78 per cent of landing area and an average elevation variation of about 169 m. The spectral analysis suggests that the region must have experienced extensive space weathering. Compositional analysis indicates that the landing region has a typical highland type of soil characteristics with Mg (4.3–5.2 wt. per cent), Fe (4.2–4.9 wt. per cent), Ca (10–11 wt. per cent), and Ti (0.25–0.35 wt. per cent). Thermophysical analyses show ∼30 and 175 K variability in spatial and diurnal temperatures at the PLS – an indicative of a local terrain of distinctive thermophysical characteristics. With important science instruments onboard, Chandrayaan-3 will provide a unique opportunity towards looking at localized variations leading to an improved understanding of the lunar surface.

Amorphous 1-propanol interstellar ice beyond its melting point

Monthly Notice of Royal Astronomical Society, 2024

The recent discovery of 1-propanol (CH3CH2CH2OH) in the interstellar medium (ISM) is of tremendou... more The recent discovery of 1-propanol (CH3CH2CH2OH) in the interstellar medium (ISM) is of tremendous interest since fatty alcohols have been proposed as constituents of proto-cell membranes. Motivated by this discovery, we present the laboratory mid- infrared (MIR) and vacuum ultraviolet (VUV) absorption spectra of 1-propanol ice under astrochemical conditions, mimicking an icy mantle on cold dust in the ISM. Both MIR and VUV spectra were recorded at ultrahigh vacuum of ∼10^-9 mbar and at temperatures ranging from 10 K to sublimation. The morphology of the 1-propanol ice deposited at 10 K was amorphous. By warming the ice to temperatures of 140 K and above, with subsequent recording of IR spectra, we observe complete sublimation of 1-propanol molecules from the substrate around 170 K. No amorphous-to-crystalline phase change was observed upon warming to higher temperatures. Additionally, we observe the IR and VUV signatures of 1-propanol ice on the substrate well beyond its melting point (147 K). To the best of our knowledge, this is the first reported observation of a molecular ice staying well beyond its melting point under such conditions. This result shows that the morphology of icy mantles on ISM cold dust grains is more complex than previously thought. Our atomistic molecular dynamics simulations capture the experimental trends and shed light on the microscopic origin of this unusual phase behaviour of 1-propanol.

Meteorite fall in Bhojade village, Kopargaon taluk, Ahmednagar district, Maharashtra, India

CURRENT SCIENCE, VOL. 124, NO. 10, 25 MAY 2023 1139, 2023

Ultraviolet spectrum reveals the presence of ozone on Jupiter's moon Callisto

Icarus, 2024

Sulphur dioxide (SO 2) is known to be present on Callisto. In this paper, we studied the chemical... more Sulphur dioxide (SO 2) is known to be present on Callisto. In this paper, we studied the chemical evolution of SO 2 astrochemical ice induced by irradiation using 9 eV (137.7 nm) vacuum ultraviolet light produced from the highflux beamline of the storage ring at the National Synchrotron Radiation Research Centre in Taiwan. Ultraviolet absorption spectra of the irradiated ice recorded in the 240-320 nm region reveal a broad absorption band indicating the formation of ozone. By comparing these laboratory spectra with Hubble Space Telescope data of the surface of Callisto in this spectral region, we find compelling evidence to consider the presence of ozone on Callisto. Furthermore, there is an additional band peaking at 309 nm whose assignment is as yet unclear but is quite similar to a band observed on Ganymede, thus leading us to suspect a common molecular source.

Optical spectroscopy of comets using Hanle Echelle Spectrograph (HESP)

MNRAS, 2024

Observing the vibrational/rotational lines in a comet’s optical spectrum requires high-resolution... more Observing the vibrational/rotational lines in a comet’s optical spectrum requires high-resolution spectroscopy, as they are otherwise seen as a blended feature. To achieve this, we have obtained medium and high-resolution (R ( λ/ dλ) = 30 000 and 60 000) spectra of several comets, including C/2015 V2 (Johnson), 46P/Wirtanen, 41P/Tuttle–Giacobini–Kres ´ak, and 38P/Stephan–Oterma, using the Hanle Echelle Spectrograph (HESP) mounted on the 2-m Himalayan Chandra Telescope (HCT) in India. The spectra effectively cover the wavelength range 3700–10 000 Å, allowing us to probe the various vibrational bands and band sequences to identify the rotational lines in the cometary molecular emission. We were also able to separate the cometary Oxygen lines from the telluric lines and analyse the green-to-red (G/R) forbidden oxygen [O I ] ratios in a few comets. For comets C/2015 V2, 46P, and 41P, the computed G/R ratios, 0.04 ±0.01, 0.04 ±0.01, and 0.08 ±0.02, respectively, point to H 2 O being a major source of Oxygen emissions. Notably, in the second fibre pointing at a location 1000 km away from the photocentre of comet 46P, the G/R ratio reduced by more than half the value observed in the first fibre, indicating the effects of quenching within the inner coma. We also measured the NH 2 ortho-to-para ratio of comet 46P to be about 3.41 ±0.05 and derived an ammonia ratio of 1.21 ±0.03 corresponding to a spin temperature of ∼26 K. With these, we present the results of the study of four comets from different cometary reservoirs using medium and high-resolution optical spectroscopy, emphasizing the capabilities of the instrument for future cometary studies.

Chandrayaan-3 APXS elemental abundance measurements at lunar high latitude

Nature, 2024

The elemental composition of the lunar surface provides insights into mechanisms of the formation... more The elemental composition of the lunar surface provides insights into mechanisms of the formation and evolution of the Moon. The chemical composition of lunar regolith have so far been precisely measured using the samples collected by the Apollo, Luna and Chang’e 5 missions, which are from equatorial to mid-latitude regions; lunar meteorites, whose location of origin on the Moon is unknown5,6; and the in situ measurement from the Chang’e 3 and Chang’e 4 missions, which are from the mid-latitude regions of the Moon. Here we report the first in situ measurements of the elemental abundances in the lunar southern high-latitude regions by the Alpha Particle X-ray Spectrometer (APXS) experiment10 aboard the Pragyan rover of India’s Chandrayaan-3 mission. The 23 measurements in the vicinity of the Chandrayaan-3 landing site show that the local lunar terrain in this region is fairly uniform and primarily composed of ferroan anorthosite (FAN), a product of the lunar magma ocean (LMO) crystallization. However, observation of relatively higher magnesium abundance with respect to calcium in APXS measurements suggests the mixing of further mafic material. The compositional uniformity over a few tens of metres around the Chandrayaan-3 landing site provides an excellent ground truth for remote-sensing observations.

Observations of the Quiet Sun during the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM: Elemental Abundances in the Quiescent Corona

The Astrophysical Journal Letters, 2021

Elements with low first ionization potential (FIP) are known to be 3-4 times more abundant in act... more Elements with low first ionization potential (FIP) are known to be 3-4 times more abundant in active region loops of the solar corona than in the photosphere. There have been observations suggesting that this observed "FIP bias" may be different in other parts of the solar corona and such observations are thus important in understanding the underlying mechanism. The Solar X-ray Monitor (XSM) on board the Chandrayaan-2 mission carried out spectroscopic observations of the Sun in soft X-rays during the 2019-2020 solar minimum, considered to be the quietest solar minimum of the past century. These observations provided a unique opportunity to study soft X-ray spectra of the quiescent solar corona in the absence of any active regions. By modeling high-resolution broadband X-ray spectra from XSM, we estimate the temperature and emission measure during periods of possibly the lowest solar X-ray intensity. We find that the derived parameters remain nearly constant over time with a temperature around 2 MK, suggesting the emission is dominated by X-ray bright points. We also obtain the abundances of Mg, Al, and Si relative to H, and find that the FIP bias is ∼2, lower than the values observed in active regions.

Multiwavelength Observations of a B-class Flare Using XSM, AIA, and XRT

We present multiwavelength observations by Chandrayaan-2/Solar X-ray Monitor, Solar Dynamics Obse... more We present multiwavelength observations by Chandrayaan-2/Solar X-ray Monitor, Solar Dynamics Observatory/ Atmospheric Imaging Assembly, and Hinode/X-Ray Telescope (XRT) of a B-class flare observed on 2021 February 25, originating from an active region (AR 12804) near the northwest limb. The microflare lasts for ∼30 minutes and is composed of hot loops reaching temperatures of 10 MK. We report excellent agreement (within 20%) for the average effective temperatures obtained at the flare peak from all the three instruments, which have different temperature sensitivities. The XRT filter combination of Be-thin and Be-med provides an excellent opportunity to measure the high temperatures in such microflare events. The elemental abundances during the evolution of the microflare are also studied and observed to drop toward photospheric values at the flare peak time, compared to coronal values during the rise and decay phase. This is consistent with previous XSM studies.

Extraterrestrial Impacts Creating Architectures for Life

J Indian Inst Sci, 2023

Prebiotic chemical evolution that led to the emergence of life on primitive Earth is interlinked ... more Prebiotic chemical evolution that led to the emergence of life on primitive Earth is interlinked with the delivery of organic material through the impact of comets, asteroids and meteorites. The catastrophic nature of impact leads to significant damage to planetary bodies. The high pressure and temperature can cause molecules to break apart and they may not survive in such extreme conditions. Also, impact-induced shock can cause impacted molecules to undergo vibration, dissociation, deformation, depending on their chemical properties and thus can offer enormous potential for the synthesis of building blocks of life. Novel experimental and theoretical approaches are required to simulate the phenomena that occur during impacts. In this brief review, we discuss impacts and related processes through laboratory experiments and simulations that study the impact-shock chemistry and its role in the Origins of Life.

X-rays in the Solar System

This chapter was originally published in the book Encyclopedia of Solar system. The copy attached... more This chapter was originally published in the book Encyclopedia of Solar system. The copy attached is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non-commercial research, and educational use. This includes without limitation use in instruction at your institution, distribution to specific colleagues, and providing a copy to your institution's administrator. All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution's website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's

Boulder Fall Ejecta: Present Day Activity on Mars

Geophysical Research Letters, 49, e2021GL096808, 2022

Boulder falls are an archives of recent surface activity on Mars, however, determining how recent... more Boulder falls are an archives of recent surface activity on Mars, however, determining how recently they fell remains elusive. Our multitemporal HiRISE image analysis shows that new tracks are characterized by a herringbone-like ejecta pattern at each boulder bounce that we call boulder fall ejecta (BFE). First systematic survey of BFE revealed ∼4,500 tracks whose total integrated track length is ∼900 km. Our BFE longevity analysis reveals that these tracks likely formed in the last few decades. From few examples we also observed slope streaks originating from BFE tracks, providing additional evidence favoring a dry origin theory. BFE fade in as little as ∼2 to 4 Mars years, whereas, others can persist >6 Mars years suggesting differential weathering. Nearly 30% of BFE are observed in the Cerberus Fossae region, which suggests it is one of the most seismically active regions. Thus, BFE can be used to recognize very recent surface processes on planetary surfaces.

Meteorite fall in Bhojade village, Kopargaon taluk, Ahmednagar district, Maharashtra, India

by Anil Bhardwaj and Dwijesh Ray

CURRENT SCIENCE, VOL. 124, NO. 10, 25 MAY 2023, 2023

The Diyodar meteorite fall in India

CURRENT SCIENCE, 152 VOL. 124, NO. 2, 25 JANUARY 2023, 2023

A study on the solar coronal dynamics during the post-maxima phase of the solar cycle 24 using S -band radio signals from the Indian Mars Orbiter Mission

by Anil Bhardwaj, Raj Choudhary, and Richa Naja Jain

Monthly Notices of the Royal Astronomical Society , 2022

Radio signals from India's Mars Orbiter Mission (MOM) have been used to study turbulence in the s... more Radio signals from India's Mars Orbiter Mission (MOM) have been used to study turbulence in the solar plasma during the post-maximum phase of solar cycle 24. S-band (2.29 GHz) radio carrier downlink signals from MOM were received at the Indian Deep Space Network, Bangalore, and frequency residuals were spectrally analysed to obtain coronal turbulence spectra at heliocentric distances ranging between 4 and 20 R , corresponding to coronal regions where the solar wind is primarily accelerated. The frequency fluctuation spectrum relates to the turbulence regime in the near-Sun region. The turbulence power spectrum (the temporal spectrum of frequency fluctuations) at smaller heliocentric distances (< 10 R) reveals flattening in lower-frequenc y re gions, with a spectral inde x α f ∼ 0.3 −0.5, which corresponds to the solar wind acceleration re gion. F or larger heliocentric distances (> 10 R), the curve steepens with a spectral index α f ∼ 0.7 −0.8, a value close to 2/3 and indicative of a developed Kolmogorov-type turbulence spectrum. The findings are consistent with earlier results. Plausible explanations to support the theory of coronal heating by magnetohydrodynamic waves and the acceleration of the solar wind are presented. An insight into the feeble maximum of solar cycle 24 is discussed.

New Signatures of Bio-Molecular Complexity in the Hypervelocity Impact Ejecta of Icy Moon Analogues

Life 2022, 12, 508, 2022

Impact delivery of prebiotic compounds to the early Earth from an impacting comet is considered t... more Impact delivery of prebiotic compounds to the early Earth from an impacting comet is considered to be one of the possible ways by which prebiotic molecules arrived on the Earth. Given the ubiquity of impact features observed on all planetary bodies, bolide impacts may be a common source of organics on other planetary bodies both in our own and other solar systems. Biomolecules such as amino acids have been detected on comets and are known to be synthesized due to impact induced shock processing. Here we report the results of a set of hypervelocity impact experiments where we shocked icy mixtures of amino acids mimicking the icy surface of planetary bodies with high-speed projectiles using a two-stage light gas gun and analyzed the ejecta material after impact. Electron microscopic observations of the ejecta have shown the presence of macroscale structures with long polypeptide chains revealed from LCMS analysis. These results suggest a pathway in which impact on cometary ices containing building blocks of life can lead to the synthesis of material architectures that could have played a role in the emergence of life on the Earth and which may be applied to other planetary bodies as well.

Processes governing the VIS/NIR spectral reflectance behavior of lunar swirls

Astronomy and Astrophysics, 639, A12, pp.1-18 , 2020

We investigated six bright swirls associated with magnetic anomalies of variable strength using C... more We investigated six bright swirls associated with magnetic anomalies of variable strength using Chandrayaan-1 Moon Mineralogy Mapper (M 3) hyperspectral image data. We examined the 3 µm absorption band generally ascribed to solar wind-induced OH/H 2 O and spectral trends in the near-infrared wavelength range at on-swirl and off-swirl locations. We found that the 3 µm absorption band is weaker at on-swirl than at off-swirl locations and shows only weak variations with time-of-day. This result is consistent with magnetic anomaly shielding that reduces solar wind interaction with the surface. For a small swirl structure in Mare Moscoviense, we found the 3 µm absorption band to be similar to that of its surroundings due to the absence of strong magnetic shielding. Our spectral analysis results at on-swirl and off-swirl locations suggest that the spectral trends at on-swirl and off-swirl locations cannot always be explained by reduced space-weathering alone. We propose that a combination of soil compaction possibly resulting from the interaction between the surface and cometary gas and subsequent magnetic shielding is able to explain all observed on-swirl vs. off-swirl spectral trends including the absorption band depth near 3 µm. Our results suggest that an external mechanism of interaction between a comet and the uppermost regolith layer might play a significant role in lunar swirl formation.

A photochemical model of ultraviolet atomic line emissions in the inner coma of comet 67P/Churyumov-Gerasimenko

Icarus, 2020

Alice ultraviolet spectrometer onboard Rosetta space mission observed several spectroscopic emiss... more Alice ultraviolet spectrometer onboard Rosetta space mission observed several spectroscopic emissions emanated from volatile species of comet 67P/Churyumov-Gerasimenko (hearafter 67P/C-G) during its entire escorting phase. The measured emission intensities, when the comet was at around 3 AU pre-perihelion, have been used to derive electron densities in the cometary coma assuming that H I and O I lines are solely produced by electron impact dissociative excitation of cometary parent species (Feldman et al., 2015). We have developed a photochemical model for comet 67P/C-G to study the atomic hydrogen (H I 1216, 1025, & 973 Å), oxygen (O I 1152, 1304, & 1356 Å), and carbon (C I 1561 & 1657 Å) line emissions by accounting for major production pathways. The developed model has been used to calculate the emission intensities of these lines as a function of nucleocentric projected distance and also along the nadir view by varying the input parameters, viz., neutral abundances and cross sections. We have quantified the percentage contributions of photon and electron impact dissociative excitation processes to the total intensity of the emission lines, which has an important relevance for the analysis of Alice observed spectra. It is found that in comet 67P/C-G, with a neutral gas production rate of about 10 27 s −1 when it was at 1.56 AU from the Sun, photodissociative excitation processes are more significant compared to electron impact reactions in determining the atomic emission intensities. Based on our model calculations, we suggest that the observed atomic hydrogen, oxygen, and carbon emission intensities can be used to derive H 2 O, O 2 , and CO, abundances, respectively, rather than electron density in the coma of 67P/C-G, when the comet has a gas production rate of 10 27 s −1 or more.

Ground calibration of Alpha Particle X-ray Spectrometer (APXS) on-board Chandrayaan-2 Pragyaan rover: An empirical approach

by Anil Bhardwaj and Swaroop Banerjee

Planetary and Space Science 187, 104923, 2020

Alpha Particle X-ray Spectrometer (APXS) was one of the scientific experiments on-board the Pragy... more Alpha Particle X-ray Spectrometer (APXS) was one of the scientific experiments on-board the Pragyaan rover of the Chandrayaan-2 mission to Moon, with the objective to determine the elemental composition of the lunar surface near the landing site in the south polar region of the Moon. APXS estimates the abundances by measuring the characteristic X-ray lines of the constituent elements present in the target surface, when irradiated by the onboard Cm-244 radioactive source. X-ray spectral measurement in the energy range of 0.8-25 keV with an energy resolution of e135 eV at 5.89 keV enables APXS to detect all the major rock-forming elements, such as Na, Mg, Al, Si, Ca, Ti, and Fe. This paper describes the calibration of APXS as an X-ray spectrometer, provides a procedure for quantitative estimation of elemental concentrations based on the measurements of standard geochemical reference materials and provides the detection limits of the major elements. It is shown that, following this procedure, the concentration of the major elements in any sample can be determined with typical accuracy of better than 10% of the actual value.

Lunar regolith and water ice escape due to micrometeorite bombardment

Icraus, 2020

Dust particles exist everywhere in interplanetary space and they evolve dynamically after their o... more Dust particles exist everywhere in interplanetary space and they evolve dynamically after their origination from the sources like Asteroid belt, Kuiper belt, comets or space debris left during the formation of solar system. These micrometeorites encounter the inner planets, while they spiral-in towards the Sun. From whichever come to Earth, many particles are ablated in the Earth's atmosphere and leave the metallic ions behind. In case of Moon, all such particles can reach the surface without ablation owing to the absence of atmosphere. Due to the impact of hypervelocity dust particles on lunar surface, ejecta come out in the lunar environment. In some cases, the ejecta velocity could be larger than the escape velocity and particles may be able to escape from Moon. Further, the escaping ejecta may carry water ice (volatiles), whenever incoming projectiles hit the surface in polar region with the water ice present. In this paper, we have computed the ejecta parameters and estimated the possible escape of volatiles from Moon, using Galileo observations of the dust particles near Moon. Considering the incident angle distribution, the upper limit of regolith escape rate is found to be ~2.218 � 10 4 [1.662 � 10 4 , 10.232 � 10 4 ] kg/s. Similarly, the upper limit of water ice escape rate is found to be ~1.988 � 10 7 [1.562 � 10 7 , 7.567 � 10 7 ] kg/s. On one side, Moon is found to be gradually becoming heavier due to its one order higher incoming dust particles than those escaping from it. While on the other side, Moon could be depleted of water ice (volatiles) resources over a period of time, because of the escape due to micrometeorite impact. The results presented here could be useful to understand the dust and volatile escape from Moon.

The dayside ionosphere of Mars: Comparing a one-dimensional photochemical model with MAVEN Deep Dip campaign observations

Icarus, 337, 113502, 2020

A one dimensional photochemical model for the dayside ionosphere of Mars has been developed for c... more A one dimensional photochemical model for the dayside ionosphere of Mars has been developed for calculating the density profiles of ions and electrons under steady state photochemical equilibrium condition. The study focuses on the Deep Dip campaigns of the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) and used the in-situ measurements of neutral density profiles, solar flux and electron temperatures from instruments onboard MAVEN as input to the model. An energy deposition model is employed for calculating the attenuated photon flux and photoelectron flux at different altitudes in the ionosphere. The Analytical Yield Spectrum approach is used for calculating the photoelectron fluxes. Volume production rates of major primary ions, CO + 2 , CO + , O + , C + , N + 2 , and N + , due to photon and photoelectron impact are calculated and used as input to the model in which ion-neutral chemistry in the dayside ionosphere is simulated. The modeled ion profiles are compared with the ion mode observations of Neutral Gas Ion Mass Spectrometer (NGIMS) and electron density estimates from Langmuir Probe and Waves (LPW). The model could reproduce the observed structure of the major ion profiles O + 2 , CO + 2 , and electron density reasonably well. However, when the magnitudes are compared, the modeled values are roughly a factor of 2 larger than observation. By reducing the neutral CO 2 density, the model outputs and the observed ion profiles and electron density profile can become closer. The model also calculated the densities of 11 other ions, viz.