scholarly journals The Lunar Fossil Figure in a Cassini State

2021 ◽  
Vol 2 (6) ◽  
pp. 232
Author(s):  
Isamu Matsuyama ◽  
Antony Trinh ◽  
James T. Keane

Abstract The present ellipsoidal figure of the Moon requires a deformation that is significantly larger than the hydrostatic deformation in response to the present rotational and tidal potentials. This has long been explained as due to a fossil rotational and tidal deformation from a time when the Moon was closer to Earth. Previous studies constraining the orbital parameters at the time the fossil deformation was established find that high orbit eccentricities (e ≳ 0.2) are required at this ancient time, which is difficult to reconcile with the freezing of a fossil figure owing to the expected large tidal heating. We extend previous fossil deformation studies in several ways. First, we consider the effect of removing South Pole−Aitken (SPA) contributions from the present observed deformation using a nonaxially symmetric SPA model. Second, we use the assumption of an equilibrium Cassini state as an additional constraint, which allows us to consider the fossil deformation due to nonzero obliquity self-consistently. A fossil deformation established during Cassini state 1, 2, or 4 is consistent with the SPA-corrected present deformation. However, a fossil deformation established during Cassini state 2 or 4 requires large obliquity and orbit eccentricity (ϵ ∼ 68° and e ∼ 0.65), which are difficult to reconcile with the corresponding strong tidal heating. The most likely explanation is a fossil deformation established during Cassini state 1, with a small obliquity (ϵ ∼ −0.2°) and an orbit eccentricity range that includes zero eccentricity (0 ≤ e ≲ 0.3).

Author(s):  
Jean Schneider ◽  
Joseph Silk ◽  
Farrokh Vakili

We address three major questions in astronomy, namely the detection of biosignatures on habitable exoplanets, the geophysics of exoplanets and cosmology. To achieve this goal, two requirements are needed: (i) a very large aperture to detect spectro-polarimetric and spatial features of faint objects such as exoplanets, (ii) continuous monitoring to characterize the temporal behaviour of exoplanets such as rotation period, meteorology and seasons. An Earth-based telescope is not suited for continuous monitoring and the atmosphere limits the ultimate angular resolution and spectro-polarimetrical domain. Moreover, a space telescope in orbit is limited in aperture, to perhaps 15 m over many decades. This is why we propose an OWL-class lunar telescope with a 50–100 m aperture for visible and IR astronomy, based on ESO's Overwhelmingly Large Telescope concept, unachievable on Earth for technical issues such as wind stress that are not relevant for a lunar platform. It will be installed near the south pole of the Moon to allow continuous target monitoring. The low gravity of the Moon will facilitate its building and manoeuvring, compared to Earth-based telescopes. We introduce a new original idea: such a large lunar telescope will allow Intensity Interferometric measurements when coupled with large Earth-based telescopes, leading to picosecond angular resolution. Rather than going into all details, our objective is essentially to inject new ideas and give a kind of roadmap. In particular, the choice of a final location will have to find a compromise between the cool temperature of craters at the Moon South Pole and the visibility of Earth for some science objectives. This article is part of a discussion meeting issue ‘Astronomy from the Moon: the next decades’.


2014 ◽  
Vol 41 (8) ◽  
pp. 2738-2745 ◽  
Author(s):  
Makiko Ohtake ◽  
Kisara Uemoto ◽  
Yasuhiro Yokota ◽  
Tomokatsu Morota ◽  
Satoru Yamamoto ◽  
...  

2005 ◽  
Vol 13 ◽  
pp. 970-970
Author(s):  
Wesley A. Traub ◽  
Antony A. Stark ◽  
Kenneth W. Jucks ◽  
Steven Kilston ◽  
Edwin L. Turner ◽  
...  

AbstractWe could observe the Earth as an extra-solar planet, viewing Earthshine on the dark side of the Moon, at the Pole, in winter.


2014 ◽  
Vol 7 (8) ◽  
pp. 569-572 ◽  
Author(s):  
Yuji Harada ◽  
Sander Goossens ◽  
Koji Matsumoto ◽  
Jianguo Yan ◽  
Jinsong Ping ◽  
...  

2009 ◽  
Vol 36 (22) ◽  
Author(s):  
Ryosuke Nakamura ◽  
Tsuneo Matsunaga ◽  
Yoshiko Ogawa ◽  
Satoru Yamamoto ◽  
Takahiro Hiroi ◽  
...  
Keyword(s):  
The Moon ◽  

Eos ◽  
2022 ◽  
Vol 103 ◽  
Author(s):  
Jure Japelj

Tidal heating may have raised the surface temperature of early Earth and triggered global volcanism, a new study says.


Author(s):  
Buddhadev Sarkar ◽  
Pabitra Kumar Mani

Aims: The Chandrayaan-2 aims to wave the Indian flag on the dark side (South Pole) of the Moon that had never been rendered by any country before. The mission had conducted to gather more scientific information about the Moon. There were three main components of the Chandrayann-2 spacecraft- an orbiter, a lander, and a rover, means to collect data for the availability of water in the South Pole of the Moon. Place and Duration of Study: The rover (Pragyan) was designed to operate for one Lunar day that is equivalent to 14 Earth days, whereas the orbiter is assumed to orbit the Moon for seven years instead of the previously planned for just one year. Overview: The Chandrayaan-2 spacecraft launched by India's heavy-lift rocket Geosynchronous Satellite Launch Vehicle-Mark III (GSLV MKIII) from the Satish Dhawan Space Center launch pad located on Sriharikota island of Andhra Prades. Unlike, Chandrayaan-1, this lunar mission aimed to perform a soft-landing on the South Pole of the Lunar surface and do scientific experiments with the help of the rover (Pragyan). Reason: The Chandrayaan-1, the first lunar mission of ISRO that detected water molecules on the Moon. The Chandrayaan-2 was a follow-on mission of Chandrayaan-1 to explore the presence of water molecules on the South Pole of the Moon. Conclusion: Although the orbiter fulfilled all of the command, unfortunately, the lander (Lander) lost its communication at the last moment to touch the Moon’s surface softly. Despite that, India again showed its potential in space missions. Chandrayaan- 2 was the most low budget lunar mission ever conducted by any space organization. The developing or even underdeveloped countries may come forward in their space program as ISRO is showing a convenient way in space missions.


2021 ◽  
Author(s):  
Marine Joulaud ◽  
Jessica Flahaut ◽  
Diego Urbina ◽  
Hemanth K. Madakashira ◽  
Gen Ito ◽  
...  

<p>Lunar volatiles, such as water, are a crucial resource for future exploration, and their exploitation should enable the use of the Moon as a platform for even more remote destinations. As water is most likely to be found in the form of ice at the lunar poles (where surface temperatures can be as low as 40K, i.e. below the H2O temperature of sublimation in vacuum, 110K), multiple upcoming missions target the south pole (SP) cold traps. PSRs (Permanently Shadowed Regions) are especially cold enough to capture and retain volatiles but present challenging access conditions (rough topography, low illumination, low temperatures, limited Earth visibility).</p><p>Funded by the EU program Horizon 2020, Space Applications Services developed the LUVMI-X rover (LUnar Volatiles Mobile Instrument eXtended), aimed at sampling and analysing lunar volatiles in the polar regions, including within a PSR. The LUVMI-X nominal payload includes an instrumented drill, the Volatiles Sampler (VS), along with a mass spectrometer, the Volatiles Analyser (VA), for surface and subsurface volatile detection and characterisation. A LIBS and a radiation detector are also included. Deployable and propellable surface science payloads are in development for inaccessible sites (e.g., some of the PSRs). This solar-powered rover has an autonomy of one or two Earth nights and can drill down to 20cm in the lunar regolith. The goal of this paper is to find suitable landing sites & traverses’ paths for this rover project, that are both scientifically interesting and technically reachable.</p><p>Available remote sensing imagery for the lunar SP was downloaded from the PDS or corresponding instruments’ websites and added into a Geographic Information System (GIS). LUVMI-X scientific objectives and technical specifications were then translated into a list of criteria and computed in our GIS using reclassifications, buffers, and intersections. Using our GIS, reclassified data were overlaid with different weights to define and rank areas meeting the compulsory criteria. A global analysis was led to select the landing sites, followed by a local analysis (based on higher resolution data) for the establishment of traverses.</p><p>The global GIS analysis allowed us to identify six regions of interest (ROI), which were compared with previous SP ROI from the literature (Lemelin, 2014; Flahaut, 2020). The identified ROI were further ranked based on areas and statistics on Sun and Earth visibilities, Diviner average surface temperatures, and H/water ice signatures (LPNS, LEND, M3).</p><p>A prime ROI located between Shackleton and the Shoemaker/Faustini ridge was selected for traverse analysis. Four landing ellipses of 2x2km were located and ranked inside the ROI. Way Points (WP) were then identified to include the following scientific interests in each traverse: a boulder casting shadows, a PSR to throw a propellable payload in, an accessible PSR to go into, etc. As several WP are possible, Earth visibility was used to select the best ones. WP were then connected by using slope maps (LOLA DEM at 5m/px: avoid slopes over 20°), Earth & Sun visibilities (avoid no-go zones) and the LROC NAC mosaics at 1m/px (avoid boulders and craters), constituting a tentative traverse.</p>


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