The moon is the most noticeable feature in the night sky and it is also the brightest, but it doesn't give off its own light. It is, actually, reflecting the light given off by the sun. Only seven percent of the light from the sun is reflected. Sometimes, the moon appears to change shape, but it is only because the sun is lighting different parts of it. When the moon passes through the earth's shadow and the earth comes right between the sun and the full moon, it's called a lunar eclipse. This is when the moon is dimmed and it turns in to a dark copper color.
When you look at the moon from earth, it looks soft with light and dark shades of blue and gray. The dark parts of the moon are extensive, flat plains that were first observed by Galileo, an Italian scientist. He was the first person to look at the moon through a telescope in 1609. He, perhaps, thought that the plains were water because he called them "maria," which is a Latin would that means Seas. Today we have discovered that they are actually huge, deep, holes with edges covered by rock and soil. The word "maria" appears to imply that there is water on the moon, but we now know that there is none on its surface.
Because there is no water on the moon, there can't be any life. Like all planets except earth, the moon has absolutely no known life. There is no water or air and the sky is continually black, but the stars are still visible. At night, the temperature on the surface of the moon becomes colder than any place on the face of the earth, but during the day, the rocks are only a slight bit hotter than that of boiling water. The Moon doesn't have an atmosphere and no fluid water, but now there is evidence that there is ice on the South Pole, which is permanently shaded. There is ice on the North Pole as well.
The Moon is Earth's only proper natural satellite. It is the fifth largest satellite in the Solar System, larger than any dwarf planet and the largest natural satellite in the Solar System relative to the size of its planet, at a quarter the diameter of Earth, comparable to the width of Australia. The Moon orbits Earth at an average lunar distance of 384,400 km (238,900 mi),or 1.28 light-seconds. Its gravitational influence produces Earth's tides and slightly lengthens Earth's day. The Moon is a differentiated rocky body; has a surface gravity of 0.1654 g, about one-sixth of Earth's; and lacks a significant atmosphere, hydrosphere or magnetic field. A planetary-mass moon, it has among satellites with a known density the second highest surface gravity and density in the Solar System after Jupiter's moon Io.
The Moon's orbit around Earth has a sidereal period of 27.3 days, and a synodic period of 29.5 days. The synodic period drives its lunar phases, which form the basis for the months of a lunar calendar. The Moon is tidally locked to Earth, which means that the length of a full rotation of the Moon on its own axis (a lunar day) is the same as the synodic period, resulting in its same side (the near side) always facing Earth. That said, 59% of the total lunar surface can be seen from Earth through shifts in perspective (its libration).
The near side of the Moon is marked by dark volcanic maria ("seas"), which fill the spaces between bright ancient crustal highlands and prominent impact craters. The lunar surface is relatively non-reflective, with a reflectance just slightly brighter than that of worn asphalt. However, because it reflects direct sunlight, is contrasted by the relatively dark sky, and has a large apparent size when viewed from Earth, the Moon is the brightest celestial object in Earth's sky after the Sun. The Moon's apparent size is nearly the same as that of the Sun, allowing it to cover the Sun almost completely during a total solar eclipse.
The first manmade object to reach the Moon was the Soviet Union's Luna 2 uncrewed spacecraft in 1959; this was followed by the first successful soft landing by Luna 9 in 1966. The only human lunar missions to date have been those of the United States' NASA Apollo program, which conducted the first manned lunar orbiting mission with Apollo 8 in 1968, and six human landings from 1969 to 1972: the first being Apollo 11 in July 1969. These missions returned lunar rocks which have been used to develop a detailed geological understanding of the Moon's origins, internal structure, and subsequent history; the most widely accepted origin explanation posits that the Moon formed about 4.51 billion years ago, not long after Earth, out of the debris from a giant impact between the planet and a hypothetical Mars-sized body called Theia.
Both the Moon's natural prominence in the earthly sky and its regular cycle of phases as seen from Earth have provided cultural references and influences for human societies and cultures throughout history. Such cultural influences can be found in language, calendar systems, art, and mythology.
The usual English proper name for Earth's natural satellite is simply the Moon, with a capital M. The noun moon is derived from Old English mōna, which (like all its Germanic cognates) stems from Proto-Germanic *mēnōn, which in turn comes from Proto-Indo-European *mēnsis "month" (from earlier *mēnōt, genitive *mēneses) which may be related to the verb "measure" (of time).
Occasionally, the name Luna /ˈluːnə/ is used in scientific writing and especially in science fiction to distinguish the Earth's moon from others, while in poetry "Luna" has been used to denote personification of Earth's moon. Cynthia /ˈsɪnθiə/ is another poetic name, though rare, for the Moon personified as a goddess, while Selene /səˈliːniː/ (literally "Moon") is the Greek goddess of the Moon.
The usual English adjective pertaining to the Moon is "lunar", derived from the Latin word for the Moon, lūna. The adjective selenian /səliːniən/,[24] derived from the Greek word for the Moon, σελήνη selēnē, and used to describe the Moon as a world rather than as an object in the sky, is rare, while its cognate selenic was originally a rare synonym[26] but now nearly always refers to the chemical element selenium. The Greek word for the Moon does however provide us with the prefix seleno-, as in selenography, the study of the physical features of the Moon, as well as the element name selenium.[28][29]
The Greek goddess of the wilderness and the hunt, Artemis, equated with the Roman Diana, one of whose symbols was the Moon and who was often regarded as the goddess of the Moon, was also called Cynthia, from her legendary birthplace on Mount Cynthus.[30] These names – Luna, Cynthia and Selene – are reflected in technical terms for lunar orbits such as apolune, pericynthion and selenocentric.
The Moon formed 4.51 billion years ago,[f] or even 100 million years earlier, some 50 million years after the origin of the Solar System, as new research suggests. Several forming mechanisms have been proposed, including the fission of the Moon from Earth's crust through centrifugal force (which would require too great an initial rotation rate of Earth), the gravitational capture of a pre-formed Moon (which would require an unfeasibly extended atmosphere of Earth to dissipate the energy of the passing Moon), and the co-formation of Earth and the Moon together in the primordial accretion disk (which does not explain the depletion of metals in the Moon). These hypotheses also cannot account for the high angular momentum of the Earth–Moon system.
The prevailing hypothesis is that the Earth–Moon system formed after a giant impact of a Mars-sized body (named Theia) with the proto-Earth. The impact blasted material into Earth's orbit and then the material accreted and formed the Moon.
The Moon's far side has a crust that is 50 km (31 mi) thicker than that of the near side. This is thought to be because the Moon fused from two different bodies.
The impact released a lot of energy and then the released material re-accreted into the Earth–Moon system. This would have melted the outer shell of Earth, and thus formed a magma ocean.[47][48] Similarly, the newly formed Moon would also have been affected and had its own lunar magma ocean; its depth is estimated from about 500 km (300 miles) to 1,737 km (1,079 miles).[47]
While the giant impact hypothesis might explain many lines of evidence, some questions are still unresolved, most of which involve the Moon's composition.[49]
When you look at the moon from earth, it looks soft with light and dark shades of blue and gray. The dark parts of the moon are extensive, flat plains that were first observed by Galileo, an Italian scientist. He was the first person to look at the moon through a telescope in 1609. He, perhaps, thought that the plains were water because he called them "maria," which is a Latin would that means Seas. Today we have discovered that they are actually huge, deep, holes with edges covered by rock and soil. The word "maria" appears to imply that there is water on the moon, but we now know that there is none on its surface.
Because there is no water on the moon, there can't be any life. Like all planets except earth, the moon has absolutely no known life. There is no water or air and the sky is continually black, but the stars are still visible. At night, the temperature on the surface of the moon becomes colder than any place on the face of the earth, but during the day, the rocks are only a slight bit hotter than that of boiling water. The Moon doesn't have an atmosphere and no fluid water, but now there is evidence that there is ice on the South Pole, which is permanently shaded. There is ice on the North Pole as well.
The Moon is Earth's only proper natural satellite. It is the fifth largest satellite in the Solar System, larger than any dwarf planet and the largest natural satellite in the Solar System relative to the size of its planet, at a quarter the diameter of Earth, comparable to the width of Australia. The Moon orbits Earth at an average lunar distance of 384,400 km (238,900 mi),or 1.28 light-seconds. Its gravitational influence produces Earth's tides and slightly lengthens Earth's day. The Moon is a differentiated rocky body; has a surface gravity of 0.1654 g, about one-sixth of Earth's; and lacks a significant atmosphere, hydrosphere or magnetic field. A planetary-mass moon, it has among satellites with a known density the second highest surface gravity and density in the Solar System after Jupiter's moon Io.
The Moon's orbit around Earth has a sidereal period of 27.3 days, and a synodic period of 29.5 days. The synodic period drives its lunar phases, which form the basis for the months of a lunar calendar. The Moon is tidally locked to Earth, which means that the length of a full rotation of the Moon on its own axis (a lunar day) is the same as the synodic period, resulting in its same side (the near side) always facing Earth. That said, 59% of the total lunar surface can be seen from Earth through shifts in perspective (its libration).
The near side of the Moon is marked by dark volcanic maria ("seas"), which fill the spaces between bright ancient crustal highlands and prominent impact craters. The lunar surface is relatively non-reflective, with a reflectance just slightly brighter than that of worn asphalt. However, because it reflects direct sunlight, is contrasted by the relatively dark sky, and has a large apparent size when viewed from Earth, the Moon is the brightest celestial object in Earth's sky after the Sun. The Moon's apparent size is nearly the same as that of the Sun, allowing it to cover the Sun almost completely during a total solar eclipse.
The first manmade object to reach the Moon was the Soviet Union's Luna 2 uncrewed spacecraft in 1959; this was followed by the first successful soft landing by Luna 9 in 1966. The only human lunar missions to date have been those of the United States' NASA Apollo program, which conducted the first manned lunar orbiting mission with Apollo 8 in 1968, and six human landings from 1969 to 1972: the first being Apollo 11 in July 1969. These missions returned lunar rocks which have been used to develop a detailed geological understanding of the Moon's origins, internal structure, and subsequent history; the most widely accepted origin explanation posits that the Moon formed about 4.51 billion years ago, not long after Earth, out of the debris from a giant impact between the planet and a hypothetical Mars-sized body called Theia.
Both the Moon's natural prominence in the earthly sky and its regular cycle of phases as seen from Earth have provided cultural references and influences for human societies and cultures throughout history. Such cultural influences can be found in language, calendar systems, art, and mythology.
The usual English proper name for Earth's natural satellite is simply the Moon, with a capital M. The noun moon is derived from Old English mōna, which (like all its Germanic cognates) stems from Proto-Germanic *mēnōn, which in turn comes from Proto-Indo-European *mēnsis "month" (from earlier *mēnōt, genitive *mēneses) which may be related to the verb "measure" (of time).
Occasionally, the name Luna /ˈluːnə/ is used in scientific writing and especially in science fiction to distinguish the Earth's moon from others, while in poetry "Luna" has been used to denote personification of Earth's moon. Cynthia /ˈsɪnθiə/ is another poetic name, though rare, for the Moon personified as a goddess, while Selene /səˈliːniː/ (literally "Moon") is the Greek goddess of the Moon.
The usual English adjective pertaining to the Moon is "lunar", derived from the Latin word for the Moon, lūna. The adjective selenian /səliːniən/,[24] derived from the Greek word for the Moon, σελήνη selēnē, and used to describe the Moon as a world rather than as an object in the sky, is rare, while its cognate selenic was originally a rare synonym[26] but now nearly always refers to the chemical element selenium. The Greek word for the Moon does however provide us with the prefix seleno-, as in selenography, the study of the physical features of the Moon, as well as the element name selenium.[28][29]
The Greek goddess of the wilderness and the hunt, Artemis, equated with the Roman Diana, one of whose symbols was the Moon and who was often regarded as the goddess of the Moon, was also called Cynthia, from her legendary birthplace on Mount Cynthus.[30] These names – Luna, Cynthia and Selene – are reflected in technical terms for lunar orbits such as apolune, pericynthion and selenocentric.
The Moon formed 4.51 billion years ago,[f] or even 100 million years earlier, some 50 million years after the origin of the Solar System, as new research suggests. Several forming mechanisms have been proposed, including the fission of the Moon from Earth's crust through centrifugal force (which would require too great an initial rotation rate of Earth), the gravitational capture of a pre-formed Moon (which would require an unfeasibly extended atmosphere of Earth to dissipate the energy of the passing Moon), and the co-formation of Earth and the Moon together in the primordial accretion disk (which does not explain the depletion of metals in the Moon). These hypotheses also cannot account for the high angular momentum of the Earth–Moon system.
The prevailing hypothesis is that the Earth–Moon system formed after a giant impact of a Mars-sized body (named Theia) with the proto-Earth. The impact blasted material into Earth's orbit and then the material accreted and formed the Moon.
The Moon's far side has a crust that is 50 km (31 mi) thicker than that of the near side. This is thought to be because the Moon fused from two different bodies.
The impact released a lot of energy and then the released material re-accreted into the Earth–Moon system. This would have melted the outer shell of Earth, and thus formed a magma ocean.[47][48] Similarly, the newly formed Moon would also have been affected and had its own lunar magma ocean; its depth is estimated from about 500 km (300 miles) to 1,737 km (1,079 miles).[47]
While the giant impact hypothesis might explain many lines of evidence, some questions are still unresolved, most of which involve the Moon's composition.[49]
चन्द्रः - Moon
नमः सूर्याय चन्द्राय मङ्गलाय बुधाय च ।
गुरुशुक्रशनिभ्यश्च राहवे केतवे नमः॥
चन्द्रः (Moon) भूमेः एकमात्र-उपग्रहः अस्ति । सूर्यस्य अनन्तरं प्रमुखं स्थानं वहति चन्द्रः भूग्रहे विद्यमानानाम् अस्माकं दृष्ट्या । भूमिः स्वं परितः भ्रमति इत्यतः चन्द्रः अपि पूर्वदिक्तः पश्चिमदिशि सञ्चरति इति भासते । अन्ये ग्रहाः इव चन्द्रेण अपि स्थिरनक्षत्रमार्गे परिपूर्णं भ्रमणं कर्तुं २७ दिनानि ७ घण्टाः ४३ निमेषाः स्वीक्रियन्ते । तन्नाम २७.३२१७ दिनानि स्वीकरोति । अयम् एव नक्षत्रमासः इति उच्यते । भूमौ स्थित्वा ये अवलोकयन्ति तेषां दृष्ट्या चन्द्रः एकस्मात् नक्षत्रात् प्रस्थाय वृत्तं समाप्य तत्रैव प्रत्यागन्तुं यावन्तं कालं स्वीकरोति सः कालः इति वक्तुं शक्यते । एषः कालः २७.३२१७ सौरदिनसमानः भवति ।
सामान्यतः चान्द्रमानः नाम अमावास्यतः अमावास्यपर्यन्तं विद्यमानः २९.५३०५८८७ सौरदिनानि इत्यर्थः । अयं कालः नक्षत्रमासात् अधिका वर्तते । चन्द्रस्य परिभ्रमणावसरे सूर्यः अपि सञ्चरति इत्यतः प्रथमामावास्यातः द्वितीयामावास्याप्राप्तिः विलम्बायते ।
भूमेः गुरुत्वाकर्षणशक्तिम् अपि यदि परिगणयेम तर्हि चन्द्रस्य कक्षा दीर्घवृत्ताकारकः भवति । अन्येषां ग्रहाणाम् उपरि रवेः आकर्षणकारणतः अस्यां कक्षायां लघु परिवर्तनं दृश्यते । भूमितः चन्द्रस्य दूरं भवति २,३८,००० मैल्-परिमितम् । इदमन्तरं २२,१०,४६० तः २,५२,७०० मैल्-परिमितं विस्तृता भवति । भूमिं परितः भ्रमन् चन्द्रः एकस्मात् समीपप्रदेशात् प्रस्थाय तत्रैव प्रत्यागमनाय यं समयं स्वीकरोति सः कालः "एनोमलिस्टिक् मासः" (anomalistic month) इति कथ्यते । अयं कालः २७.५५४६ सौरदिनसमं भवति । चन्द्रस्य कक्षा भूचक्रात् अधिकतरं नाम ५ डिग्रि १५ कोणे नत्वा भ्रमति ।
वायुमण्डलम्
सान्द्रता
प्रति से.मी२ कृते १०७ कणाः (दिने)
प्रति से.मी२ कृते २०५ कणाः (रात्रौ)
एषः भूमेः एकैकं नैसर्गिकः उपग्रहः । भूग्रहस्य एवम् चन्द्रस्य मध्ये सर्वसामान्यदूरम् ३८४,३९९ कि.मी.यावत् एतस्मात् दूरात् चन्द्रेण प्रतिफलितः प्रकाशः भूमिं प्राप्तुं सामान्यतः २३ क्षणानि आवश्यकानि । चन्द्रस्य व्यासः ३,४७४ कि.मी परिमितं भवति (२,१५९ मैल्) (भूग्रहात् ३.७ गुणितम् न्यूनम् ।) एषः सौरमण्डलस्य पञ्चमः अतिभारयुकः तथा अतिविस्तृतः उपग्रहः । ग्यानिमिड्ड्, टैटन्, क्यालिष्टो, एवं ऐओ चन्द्रात् बृहत् उपग्रहाः । सागरस्य उत्कर्षापकर्षयोः चन्द्रस्य गुरुत्वाकर्षणमेव कारणम् । एकवारं भूमिं परितः परिभ्रमणं कर्तुम् एषः २७.३ दिनानि स्वीकरोति । भूमि-चन्द्र-सूर्याणां व्यवस्थायाम् आवर्तमानेभ्यः परिवर्तनेभ्यः चन्द्रस्य कलाः सम्भवन्ति । एताः कलाः २७.५ दिनेषु एकवारम् आवर्तिताः भवन्ति । भूमिं विहाय मानवैः यत्र पदं न्यस्तं तादृशः एकैकः आकाशकायः नाम चन्द्रः । रष्यादेशस्य लूनयोजनायाः गगननौका तावत् चन्द्रग्रहं प्रति ऐदम्प्राथम्येन प्रेषिता मानवर्राहतगगननौका। लूना-१ भूगुरुत्वं अतीत्य चन्द्रस्य समीपं गतवत् प्रथमं मानवेन निर्मितं वस्तु । लुना-२ चन्द्रस्य बाह्यस्तरं प्रति प्रेषितं प्रथमं मानवनिर्मितं वस्तु । सामान्यतः अस्माकं दर्शनेन विमुखस्य चन्द्रस्य अपरमुखम् लूना-३-द्वारा चित्रीकृतम् । एतत्सर्वम् १९५९ तमे वर्षे जातम् । चन्द्रस्य उपरि पदं न्यस्तवत् प्रथमं मानवर्राहतम् नौकायानं लूना ९। एवं चन्द्रस्य परिभ्रमणं कृतम् प्रप्रथमनौकायानम् लूना -२० । १९६६तमे वर्षे अमेरिका-संस्थानस्य अपोलोयोजनायाः अङ्गतया चन्द्रस्य उपरि प्रथमं मानवसहितं नौकायानं १९६८ तमे वर्षे चन्द्ं परितः भ्रमणम् अकरोत् । अनन्तरं १९६९ तमे वर्षे अपोलो- २२ मानवस्य साक्षात् चन्द्रस्य उपरि पादार्पणम् अकारयत् । एषः मनुकुलस्य इतिहासे स्वर्णाक्षरैः लेखितुम् योग्यः कार्यक्रमः आसीत् । एवम् १९६८ तमे आरब्धा अपोलोयोजना मानवस्य चन्द्रस्योपरि पादार्पणेन १९६९ तमे वर्षे परिसमाप्तिं गता । तथापि भविष्ये चन्द्रस्य दिशि मानवसहित /रहितगगननौकायानानां प्रेषणे अनेकेदेशाः प्रयतन्ते स्म। मङ्गलग्रहस्य यात्रार्थं चन्द्रस्योपरि एकं शाश्वतं गगननौकास्थानं स्थापयितुं डिसेम्बरमासस्य ४ दिनाङ्के २००६ वर्षे नासासंस्थया सूचना दत्ता । निर्माणकार्ये पञ्चवर्षीणि अपेक्षितानि भवेयुः इति निरीक्षा वर्तते । तदनन्तरं २०२० तमे वर्षे प्रथम-अन्तरिक्षयानानाम् आरम्भः भवेत् इति निरीक्ष्यते ।
चन्द्रस्य मुखद्वयम्
चन्द्रः समकालिकपरिभ्रमणं कुर्वन् भवति इत्यतः तस्य एकमेव मुखं सर्वदा अस्माभिः दृश्यते । बहुपूर्वं भूमेः उपरि जायमानैः सागराणाम् उत्कर्षापकर्षैः चन्द्रस्य अक्षीयपरिभ्रमणं मन्दं जातं सत् तदधीनम् अभवत् । तथापि चन्द्रस्य कक्षाकेन्द्रय्युतिकारणात् जातैः लघु परिवर्तनैः वयं चन्द्रस्य ५९% बाह्यस्तरं दृष्टुं शक्नुमः । एतत् मुखम् ‘पुरोमुखम्’ इति तस्य विरुद्धदिशायां वर्तमानः भागः “पृष्टमुखम्’ इति कथयन्ति । पूर्णिमायां चन्द्रस्य पुरोमुखं दृष्तं चेत् अपरमुखे अमावास्या भवति । अमावास्यायाम् अदृश्यमुखे पूर्णिमा भवति।
समतलप्रदेशाः
चन्द्रस्य उपरि विद्यमाना गाढा तीक्ष्णा तथा वैशिष्ट्यरहिता या भूमिः अस्ति सा ‘मेर्’ इति नाम्ना निर्दिश्यते । ‘मेर’ इत्यस्य ल्याटिन्भाषया समुद्रः इत्यर्थः । एते वलयाः जलेन आवृत्ताः इति विश्वस्य ‘मेर्’ इति नाम प्रदत्तम् । वास्तवरूपेण एते विस्तृताः कृष्णशिलायाः लावाप्रवाहाः । एते सर्वे चन्द्रस्य पुरोमुखे एव दृश्यन्ते । पृष्ठभागे (तिरोमुखे)अधिकतया न दृश्यन्ते । पृष्ठभागस्य २% विस्तीर्णमात्रम् अनेन आवृतम् । पुरोभागस्य ३२% विस्तीर्णप्रदेशः ‘मेर्’ प्रदेशेन आवृत्तः । पुरोमुखे तत्र तत्र ज्वालमुख्यः सन्ति । एतस्य भेदस्य अत्यन्तं सम्भवनीयं कारणं नाम- पुरोमुखे शाखोत्पन्नसमर्थानि वैशिष्ट्यानि सान्द्राणि सन्ति । एतादृशानि वैशिष्ट्यानि लूनार् प्रास्पेक्टर्न् गामाकिरणानां वर्णमापकपटलैः प्राप्त्ताभिः भूरासायनिकनक्षाभिः ज्ञायन्ते । पुरोभागे बहुत्र ज्वालामुख्यः सन्ति ।
उन्नतप्रदेशाः
एते समभागात् उन्नतस्तरे सन्ति इत्यतः एतेषां ‘टेरे’ इति नाम प्रदत्तम् । पुरोमुखे अनेके उन्नतपर्वतश्रेणयः बाह्य परिधौ दरीदृश्यन्ते । भूफलकस्य चलनात् अत्र यथा पर्वताः निर्मिताः तथा चन्द्रस्य एते पर्वताः निर्मिताः न सन्ति ।
सङ्घट्टितगर्ताः
चन्द्रस्य उपरि सर्वत्र एते सङ्घट्टनेन जाताः गर्ताः दृशन्ते । एते धूमकेतूनां सङ्घट्टनात् शतकोटिवर्षपूर्वम् सञ्जाताः ।। १ कि.मीटरात् अपि अधिकव्यासपरिमिताः ५ लक्षाधिकाः गर्ताः चन्द्रस्योपरि द्रष्टुं शक्याः वायुमण्डलस्य अनुपस्थितेः कारणात् एते नूतनाः इव दृश्यन्ते। चन्द्रस्य बाह्यमुखे स्थिताः मुख्यगर्ताः एवं सन्ति- इम्ब्रियं, सेरेनिटाटिस् , क्रिसियं, नेक्टारिस्गा इति ।
जलस्य अस्तित्वम्
धूमकेतूनाम् उल्कापिण्डानां सङ्घट्टनात् किञ्चित् जलस्य खण्डाः चन्द्रस्योपरि सञ्चिताः अभवन् । एते सूर्यकिरणैः आम्लजनक-जलजनकरुपेण विभक्ताः भूत्वा बाह्माकाशं गच्छन्ति । अपोलोगगनयात्रिभिः समभाजकस्य समीपे शिलाखण्डेषु सङ्गृहीतः अत्यल्पप्रमाणकः जलस्य अंशः संशोधितः अस्ति। एतेन ज्ञायते यत् अत्र जलस्य अंशः नास्ति इति। किन्तु ध्रुवस्य समीपे जलकणाः स्युः इति ऊहयते । दक्षिणध्रुवप्रदेशे २४,००० च. कि.मी प्रदेशः शाश्वतछायायां स्यात् इति गणकीकृतछायाचिव्राणि सूचयन्ति । उपयोक्तुं योग्यप्रमाणेन जलस्य अस्तित्वं चन्द्रे जनवासार्थं मुख्यः विषयः भवति।
गुरुत्वक्षेत्रम्
चन्द्रस्य गुरुत्वक्षेत्रस्य प्रमुखं वैषिष्ट्यं नाम यत्र महता प्रमाणेन सङ्घट्टनं जातम् अस्ति तत्र गमनार्हरूपेण गुरुत्वे असमञ्जसता वर्तते । एताम् असमञ्जसतां ‘म्यास्गान्’ इति कथयन्ति । एतादृशी असमञ्जसता गगननौकायाः कक्षायाः निर्धारणे अधिकं प्रभावं जनयन्ति। किन्तु मानवसहित/रहितचन्द्रयानस्य सज्जतायां निखरगुरुत्वस्य ज्ञानम् अत्यावश्यकम् अस्ति । यतः अपोलोनौकाचालनस्य पूर्वपरीक्षायां, गगननौकावतरणस्थानानि निरीक्षायाः अपेक्षया भिन्नानि जातानि । अस्य समस्यायाः कारणं किम् इति अन्विष्य परिभ्रामकेण सूचना प्रेषिता । कारणं गुरुत्वस्य असमञ्जसता इति ज्ञातमभूत्।
कान्तक्षेत्रम्
चन्द्रस्य बाह्यकान्तक्षेत्रं बहुदुर्बलम् । चन्द्रः प्रस्तुतं द्विध्रुवकान्तक्षेत्रं न प्राप्तवान् अस्ति । यतः तस्य अन्तः उत्पादकाः लावारसादयः न सन्ति। चन्द्रस्य प्रस्तुतकान्तक्षेत्रं सम्पूर्णतया बाह्य-आवरणेन उद्भूतम् । प्लस्मामेघस्य कारणात् अस्थिरकान्तक्षेत्राणि उद्भवन्ति इति सूचितम् अस्ति ।
वायुमण्डलम्
चन्द्रः सामान्यतया विरलं निर्वातरुपं वायुमण्डलम् विदधाति । चन्द्रस्य आन्तरिकभागेषु उत्पादितेभ्यः विकिरण क्षयेभ्यः ‘टेडान्’ इत्यादयः अनिलाः उद्भवन्ति । सौरमारुतात्, सूर्यकिरणात् च अनिलाः अल्पप्रमाणेन उत्पन्नाः भवन्ति । एते अनिलाः बाह्याकाशे मारुतस्य कान्तक्षेत्रात्, सौरमारुतस्य आकुञ्चनात् वा विनष्टाः भवेयुः । वर्णपटलमापकद्वारा चन्द्रस्य उपरि सोडियं (Na), पोट्याषियं (K) मूलवस्तूनि संशोधितानि सन्ति ।
उद्भवः भूवैज्ञानिकविकसनञ्च
समकालिक-उद्भववादानुसारं सूर्यं परितः यथा ग्रहाः उद्भूताः, तथा भूमिं परितः चन्द्रः उद्भूतः । किन्तु चन्द्रस्य उपरि अयसः न्यूनताकारणतः एषः वादः सर्वैः नाङ्गीक्रियते । किन्तु ‘बृहत् सङ्घट्टनसिद्धान्तं सर्वे सामान्यतया अङ्गीकुर्वन्ति । मङ्गलग्रहसदृशः आकाशकायः भूमिं घट्टयति, (‘थीय’ अथवा ‘आर्फयस्’ इति तस्य नाम) अनेन घट्टनसमये उद्भूतपदार्थानां सम्मेलनेन चन्द्रः निर्मितः इति अस्य सिद्धान्तस्य आशयः । तथापि चन्द्रस्य निर्माणे आवश्यकाः पदार्थाः कस्मात् अनुपातात् भूम्याः, एवं बाह्य-आकाशकायात् (‘आर्फियस्’ कायात्) आगताः इति सन्देहः विद्यते एव । चन्द्रस्य निर्माणं ४५२.७+- १ कोटि वर्षात् पूर्वं जातम् । सौरमण्डलस्य उद्भवात् ३-५ कोटि वर्षेभ्यः अनन्तरं इति परिगणयन्ति ।
चन्द्रस्य शिलापाकसागरः
महासङ्घट्टनात्, तदनन्तरतनसञ्चयनात् अपारशक्तिः आविर्भूता अभवत्। । एतादृशबहु-उष्णशक्तेः कारणात् चन्द्रस्य बहुभागः द्रवरुपेण आसीत् इति चिन्तयन्ति। द्रवस्यास्य बाह्यभागः ‘चन्द्रस्य शिलापाकसागरः’ इति कथ्यते । अस्य गभीरता ५०० कि.मी परिमिता सती चन्द्रस्य केन्द्रपर्यन्तम् आसीत् इति ऊहा अस्ति ।
भूवैज्ञानिकविकसनम्
चन्द्रस्य बाह्य परिधेः ३ कि.मीटरात्मकः व्यासवलयः २० लक्षवर्षेभ्यः पूर्वं अनिलबाह्यप्रसरणात् व्यत्यस्तः इति वदन्ति ।
कक्षया एवं भूम्याः साकम् सम्वन्धः
२७.३ दिनेषु एकवारं चन्द्रः भूमिं परितः परिभ्रमति (चन्द्र्स्य नाक्षत्रिक अवधिः)। किन्तु भूमिरपि सूर्यस्य परिभ्रमणं स्वकक्षायां करोति अतः चन्द्रस्य ताः एव कलाः अस्माभिः २७.५ दिनेषु दृश्यन्ते (चन्द्रस्य यति-अवधिः) चन्द्रः भूमेः क्रान्तिवृत्तस्य समतलस्य समीपे परिभ्रमति समुद्रस्य उत्कर्षापकर्षं विहायापि भूमिचन्द्रयोः मध्ये परस्परं अनेके परिणामाः भवन्ति । अनेन उत्कर्षापकर्षाभ्यां भूमि – चन्द्रयोः सर्वसामान्यदूरं शतके ४ मीटर् अथवा प्रतिवर्षम् ४ से.मी अधिकं भवति ।
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