Our solar system, consisting of the Sun, planets, Moons, asteroids, and comets, along with gas, dust, ice, and radiation, is a very complex and dynamic system. Globally, planetary, astronomy, and small-body exploration programs have made great strides in understanding the formation and evolution of stellar systems while also providing detailed views of individual bodies. The forthcoming decades offer immense opportunities for planetary exploration from space and observations from ground telescopes that portend to very significantly expand not only the horizons of human exploration but also provide a more fundamental understanding of the evolutionary pathways that led to the myriad diversity in our Solar System. The past, present, and future of the solar system also serve as a Rosetta stone to decipher the physics, chemistry, and biology of the exo-planetary systems. Here, we recommend solar system exploration objectives for the decade and beyond in the context of current global developments in the field and research groups in India.

Ground-Penetrating Radar (GPR) provides high-resolution, non-invasive insights into the subsurface, making it an essential tool for assessing climate change impacts and managing infrastructure in Arctic and sub-Arctic environments. This review examines GPR applications in mapping and characterizing cold-region features to enhance our understanding of the Critical Zone at high latitudes. Specifically, we focus on permafrost, including its active layer and embedded ice structures, as well as glaciers and front moraine, ice sheets, and snow cover. Furthermore, driven by advancements in miniaturization and energy efficiency, we extend our review to GPR-based subsurface exploration on the Moon and Mars, where environmental conditions and frozen geomorphological structures share similarities with terrestrial cold regions. Finally, we highlight the interconnection between hardware and software advancements and the expanding applications of GPR in cryospheric research.

Subsurface exploration of ice-covered planets and moons presents communications challenges because of the need to communicate through kilometers of ice. The objective of this task is to develop the capability to wirelessly communicate through kilometers of ice and thus complement the potentially failure-prone tethers deployed behind an ice-penetrating probe on Ocean Worlds. In this paper, the preliminary work on the development of wireless deep-ice communication is presented and discussed. The communication test and acoustic attenuation measurements in ice have been made by embedding acoustic transceivers in glacial ice at the Matanuska Glacier, Anchorage, Alaska. Field test results show that acoustic communication is viable through ice, demonstrating the transmission of data and image files in the 13-18 kHz band over 100 m. The results suggest that communication over many kilometers of ice thickness could be feasible by employing reduced transmitting frequencies around 1 kHz, though future work is needed to better constrain the likely acoustic attenuation properties through a refrozen borehole.

Remote-sensing observations on the surface of airless bodies, such as the Moon and asteroids, have confirmed the presence of hydrogen-bearing materials. However, their spatial distributions at small scales (mm-m) and depth profiles have great uncertainties. In-situ analyses of hydrogen-bearing materials with laser-induced breakdown spectroscopy (LIBS) have been proposed to resolve these problems, as the footprint of LIBS ablation is small (less than or similar to 1 mm) and can penetrate into the subsurface by excavating the surface layer. Nevertheless, the measurement accuracy of hydrogen with LIBS on airless and hydrous planetary bodies has not been evaluated because it requires extensive calibration using hydrogen-rich geologic materials under a high-vacuum condition. In addition, whether hydrogen occurs as hydroxyl or ice has been difficult to ascertain via LIBS analysis because molecular information is typically lost in the ablation plasma. To resolve these problems, we conducted two experiments. First, compressed powders of rocks were measured by LIBS under vacuum (<3 x 10(-2) Pa) to evaluate the calibration accuracies and detection limits in rocks and compacted soils on airless bodies. Several geostandards including basalts and feldspars were doped with various concentrations of hydroxyls (Mg(OH)(2) and Ca(OH)(2)) to prepare hydrogen-rich samples up to 15 wt% in H2O-equivalent concentration (wt%H2O). Our results show that the hydrogen concentration can be accurately calibrated from the LIBS spectra by using multivariate models or matrix-matched calibration curves (i.e., calibration using samples with comparable bulk elemental abundances), facilitating the correction of significant matrix effects observed in the intensities of the 656 nm Ha line. We obtained a measurement accuracy of +/- 0.9 wt%H2O in the 0-12 wt%H2O range via matrix-matched calibration. This level of accuracy is sufficient for many planetary and resource exploration applications, such as designing hardware and operation for mining water on the Moon. We estimate the 2 sigma limit of detection (LOD) to be 0.4 wt %H2O based on the average of all samples, although better LODs were obtained for some individual matrix (e.g., 0.2 wt%H2O for basalt/feldspar-Ca(OH)(2) mixtures). Such LOD shows that exploitable ice on the Moon can be detected with 2 sigma confidence by LIBS. Second, we demonstrate that the molecular structure of hydrogen can be distinguished by operating LIBS in tandem with heating lasers. In this method, the samples are heated prior to LIBS analysis using a continuous-wave laser with adjusted fluence and duration. Our results indicate that ice and hydroxyl can be distinguished because the Ha lines of ice-bearing samples decrease after the laser heating due to sublimation, but those of hydroxyl-bearing samples are retained. In addition, we report an enhancement of hydrogen emission from loose powders, suggesting that hydrogen in lunar soils may be measured with higher sensitivity. The results of this study show that LIBS is a versatile and powerful tool for accurate stand-off measurement of hydrogen-bearing materials on airless planetary bodies.

The comparative study of planetary systems is a unique source of new scientific insight: following the six key science questions of the Planetary Exploration, Horizon 2061 long-term foresight exercise, it can reveal to us the diversity of their objects (Question 1) and of their architectures (Question 2), help us better understand their origins (Question 3) and how they work (Question 4), find and characterize habitable worlds (Question 5), and ultimately, search for alien life (Question 6). But a huge knowledge gap exists which limits the applicability of this approach in the solar system itself: two of its secondary planetary systems, the ice giant systems of Uranus and Neptune, remain poorly explored.Starting from an analysis of our current limited knowledge of solar system ice giants and their systems in the light of these six key science questions, we show that a long-term plan for the space exploration of ice giants and their systems will greatly contribute to answer these questions. To do so, we identify the key measurements needed to address each of these questions, the destinations to choose (Uranus, Neptune, Triton or a subset of them), the combinations of space platform(s) and the types of flight sequences needed.We then examine the different launch windows available until 2061, using a Jupiter fly-by, to send a mission to Uranus or Neptune, and find that:(1) an optimized choice of platforms and flight sequences makes it possible to address a broad range of the key science questions with one mission at one of the planets. Combining an atmospheric entry probe with an orbiter tour starting on a high-inclination, low periapse orbit, followed by a sequence of lower inclination orbits (or the other way around) appears to be an optimal choice.(2) a combination of two missions to each of the ice giant systems, to be flown in parallel or in sequence, will address five out of the six key questions and establish the prerequisites to address the sixth one: searching for life at one of the most promising Ice Giant moons.(3) The 2032 Jupiter fly-by window, which offers a unique opportunity to implement this plan, should be considered in priority; if this window cannot be met, using the 2036 Jupiter fly-by window to send a mission to Uranus first, and then the 2045 window for a mission to Neptune, will allow one to achieve the same objectives; as a back-up option, one should consider an orbiter + probe mission to one of the planets and a close fly-by of the other planet to deliver a probe into its atmosphere, using the opportunity of a future mission on its way to Kuiper Belt Objects or the interstellar medium;(4) based on the examination of the habitability of the different moons by the first two missions, a third one can be properly designed to search for life at the most promising moon, likely Triton, or one of the active moons of Uranus.Thus, by 2061 the first two missions of this plan can be implemented and a third mission focusing on the search for life can be designed. Given that such a plan may be out of reach of a single national agency, international collaboration is the most promising way to implement it.

One of NASA priorities is the in-situ exploration of ocean worlds in the solar system where potentially there might be life under the ice shell. This requires reaching the ocean below extremely cold through significant deep ice. Jupiter's moon, Europa, is such a challenging body, where it is estimated to have a 40 km thick ice shell. An approach for reaching the ocean has been conceived using a melting probe Cryobot concept that has been studied for a potential future mission. A lander is assumed to be the platform from which the Cryobot would be deployed. The ice penetrating vehicle concept consists of a cylindrical, narrow-body probe that encases a radioisotope heat/power source that would be used to do the penetration by melting through the icy crust. The baseline design of the probe includes a suite of science instruments to analyze the ice during descent and the liquid ocean underneath. For communication, a set of fiber optic wire as well as wireless RF in the very cold porous top layer is assumed, and then acoustic modules would be used for the communication in warmer denser ice over distance of 25 km between the modules. In addition to the acoustic communication modules, a sonar is part of the concept, for obstacle avoidance. The focus of this paper is on the use of elastic waves in the 1kHz range.

The quest for life on other planets is closely connected with the search for water in liquid state. Recent discoveries of deep oceans on icy moons like Europa and Enceladus have spurred an intensive discussion about how these waters can be accessed. The challenge of this endeavor lies in the unforeseeable requirements on instrumental characteristics both with respect to the scientific and technical methods. The TRIPLE/nanoAUV initiative is aiming at developing a mission concept for exploring exo-oceans and demonstrating the achievements in an earth-analogue context, exploring the ocean under the ice shield of Antarctica and lakes like Dome-C on the Antarctic continent.

Ocean worlds is the label given to objects in the solar system that host stable, globe-girdling bodies of liquid water-oceans. Of these the Earth is the only one to support its oceans on the surface, making it a model for habitable planets around other stars but not for habitable worlds elsewhere in the solar system. Elsewhere in the solar system, three objects Jupiter's moon Europa, and Saturn's moons Enceladus and Titan have subsurface oceans whose existence has been detected or inferred by two independent spacecraft techniques. A host of other bodies in the outer solar system are inferred by a single type of observation or by theoretical modeling to have subsurface oceans. This paper focusses on the three best-documented water oceans beyond Earth: those within Europa, Titan and Enceladus. Of these, Europa's is closest to the surface (less than 10 km and possibly less than 1 km in places), and hence potentially best suited for eventual direct exploration. Enceladus' ocean is deeper 5-40 km below its surface but fractures beneath the south pole of this moon allow ice and gas from the ocean to escape to space where it has been sampled by mass spectrometers aboard the Cassini Saturn Orbiter. Titan's ocean is the deepest perhaps 50-100 km-and no evidence for plumes or ice volcanism exist on the surface. In terms of the search for evidence of life within these oceans, the plume of ice and gas emanating from Enceladus makes this the moon of choice for a fast-track program to search for life. if plumes exist on Europa yet to be confirmed or places can be located where ocean water is extruded onto the surface, then the search for life on this lunar-sized body can also be accomplished quickly by the standards of outer solar system exploration.

A Wireless Sensor Network for in situ probing of lunar water/ice is proposed. The mission scenario in single and multi-tier architectures for probing water in a permanently shadowed region of the Moon and different scenarios of exploration are discussed. The ideas presented in the paper are a positive assertion of feasibility for the sensor node hardware, given current levels of technological advancements. (C) 2011 COSPAR. Published by Elsevier Ltd. All rights reserved.

Chandrayaan-1, the first Indian planetary exploration mission, will carry out high resolution remote sensing studies of the moon to further our understanding about its origin and evolution. Hyper-spectral imaging in the UV-VIS-NIR region using three imaging spectrometers, along with a low energy X-ray spectrometer will provide mineralogical and chemical composition of the lunar surface at high spatial resolution. A terrain mapping camera will provide high resolution three-dimensional images of the lunar surface and will be complemented by a laser ranging instrument that will provide lunar altimetry. Three payloads - a high energy X-gamma ray spectrometer, a sub-keV atom reflecting analyser, and miniature imaging radar - will be used for the first time for remote sensing exploration of a planetary body. They will investigate transport of volatiles on the lunar surface, presence of localized lunar mini-magnetosphere and possible presence of water ice in the permanently shadowed lunar polar region respectively. A radiation dose monitor will provide information on energetic particle flux en route to the moon and in lunar orbit. An impact probe carrying an imaging system, a radar altimeter and a mass spectrometer will be released from the spacecraft to land at a predestinated lunar site. The design of the one tonne-class spacecraft is primarily adapted from flight proven Indian Remote Sensing satellite bus with several modifications that are specific to the lunar mission. The spacecraft was launched by using a variant of the indigenous Polar Satellite Launch Vehicle (PSLV-XL) and placed in a 100 km circular polar orbit around the moon with a planned mission life of two years. An Indian Deep Space Network and an Indian Space Science Data Center have been established as a part of Chandrayaan-1 mission and will cater to the need of future Indian space science and planetary missions.