Earth's Moon: Mythology and Exploration

• The book is targeted for high school students.
• It describes Earth's moon, including evolution, understanding, and exploration, highlighting the scientific aspects.

Moon in Mythology

• The moon is one of humanity's oldest companions, documented in the mythologies of nearly all civilizations.
• In Indian mythology, the moon is a deity.
• The Rigveda contains prayers to the moon deity for wisdom and intellect.
• Ancient Indian cultures worshipped both the sun and the moon, recognizing the importance of understanding their mystery through intellect and wisdom, which is now recognized by planetary scientists.
• The moon has been depicted as both male and female deities in mythology, such as the Greek goddess Selene, the Roman goddess Luna, and the Chinese goddess Chang'e.
• Some civilizations personified the Moon as a male deity, including Sin of the Mesopotamians, Mani of Germanic tribes, Tsukuyomi of the Japanese, and Igaluk/Alignak of the Inuit people.
• Many moon missions derive their names from mythological lunar deities, like the Indian deity Chandra.

Moon in Human Civilization

• The moon has served as a timekeeper since ancient times.
• It has influenced the almanac, agriculture, literature, moods, and psyche, making it an integral part of human existence.
• The Moon inspired emotions like romance and fear through demonic characters.
• Agriculture based on lunar cycles, high and low tides, and human body responses are tuned to the moon's rhythm.

The Dark Spots on the Moon

• Ancient sky-gazers depended on observations with bare eyes, and were curious about the dark patches on the moon's surface.
• With the invention of the telescope in the early seventeenth century, the horizon of observations expanded, marking astronomy's birth.
• Galileo's first telescope presentation was celebrated 400 years ago.
• Thomas Harriot used an optical telescope to sketch the moon before Galileo, on July 26, 1609.
• The moon's surface has 2 distinct features - dark and bright regions.
• The dark regions on the moon's surface resembled oceans and were named 'Maria' which meant ocean.
• Lunar missions then used instruments to accurately measure the heights and depths of the undulations on the moon's surface.
• Maria regions were observed as flat, other regions were called highlands due to higher elevation.
• Maria constitutes 17% of the moon’s surface.

The Highlands and the Mare Regions

• The 'Maria' or 'Mare' regions are volcanic plains composed of basalt.
• The highlands resemble a series of hills or mountains.
• The 'Maria' or 'Mare' region looks like a water body or a pond.
• Molten lava of volcanic origin filled the areas during the formative days of the moon.
• Lunar maria are volcanic plains covering about 17% of the Moon's surface.

The Uniqueness of our Moon

• The moon is the Earth's only natural satellite.
• Humans have created artificial satellites for communication, imaging, remote sensing and navigation.
• The Solar System has eight planets and one dwarf planet called Pluto, some with natural satellites.
• Earth's moon is unique compared to other satellites in the solar system.
• Other solar system satellites are thousands of times lighter than their respective planets.
• The moon is only 80 times lighter than Earth.
• The moon is massive enough to have significant gravitational influence on Earth.

Major Influences of the Moon on Earth

• The mass of the Moon is substantial as compared to Earth, and the Earth and Moon contribute mutually to their relative motion.
• This mutual contribution forms a two-body problem with substantial contributions to collective dynamics.
• It is believed that the moon gravitationally stabilized the orbit of the Earth, and it also facilitated an equitable climate on Earth.
• Wobbling of the Earth would have caused extreme temperature conditions.
• Gravitation reduces the Earth's spin, producing tidal effects (~2-5h to ~24-h period).
• Lunar tides brought marine life from seas to land, where life evolved into land species.

Comparison between Moon and Earth

• The moon has less atmosphere than Earth.
• Earth has about 10^19 air atoms/molecules per cubic centimeter, whereas the moon has only approximately 10^5 atoms/molecules during the day, and 10^3 atoms/molecules during the night.

Atmosphere content on Earth

• Earth's atmosphere: 78% Nitrogen, 21% Oxygen, and Argon, Carbon Dioxide and trace constituents.
• The moon has varying atmospheric pressure, there is a factor-of-hundred difference in pressure during lunar day and night and the composition of air also changes.
• The composition of the moon’s atmosphere and its variability is actively researched today.
• Lunar days can be 120 degrees Centigrade, while lunar nights may be -180 degrees Centigrade, a 300 degrees difference.
• The Earth has a geomagnetic field but the moon does not have a field.
• The moon features small localized regions shielded by magnetic fields ('mini-magnetospheres') with a size of a few hundred kilometers.
• Refrigerator magnets produce ~10 milli Tesla.
• Earth’s magnetic field is ~35,000 nano Tesla.
• Mini-magnetosphere is ~100 nano Tesla.

Lunar Eclipse

• A lunar eclipse occurs when Earth's shadow falls on the moon.
• This can only happen when the Earth is between the Sun and the Moon.
• The Earth’s orbit around the sun is not in the same plane as the Moon's orbit around the Earth, it is tilted by an angle of ~5.145 degrees.

Phases of the Moon: The Concept of Synodic Period

• The sun illuminates half of the moon, with other half in darkness.
• The side we see from earth may not be directly illuminated fully.
• The fraction of the illuminated side is visible as the moon travels its orbit around the Earth, which makes Lunar phases.
• The earth rotates around the sun, and the moon rotates around the Earth.
• The determining phase of the Moon is the sun-moon-observer on Earth angle, which is also called the phase angle.
• The phases progresses from New Moon, Waxing Crescent, first quarter, Waxing Gibbous, Full Moon, Waning Gibbous, last quarter, Waning Crescent, till the next New Moon phase.
• 'Waxing' indicates progress towards Full Moon.
• 'Waning' indicates progress toward New Moon.
• The Synodic period is the time between two new moons a lunar month amounts to 29.5 days.

Motion of Earth and Moon Relative to the Sun: The Concept of Sidereal Period

• Moon's Sidereal period is the time it takes to orbit 360 degrees around the Earth relative to a fixed star.
• Moon's sidereal period is 27.3 days.
• Completion of one sidereal period does not ensure that the Moon’s phase.
• The moon takes two extra days in its orbit to complete its phase cycle, this is because the Earth orbits the sun.

Tidal Locking

• Earth views only one side of the moon.
• The moon spins, although its spin rate is slower than Earth.
• One lunar day is about 14 earth days.
• The moon always shows one side to Earth.
• Gravitational attraction may deform both bodies, leads to 'tidal bulges' on either side, but if misaligned, leads to realignment.
• Tidal bulges lead to synchronism of spinning and orbital rotation frequencies.

Nearside and Farside of the Moon

• The Earth only sees one side of the moon referred to as the 'nearside' and the other side is the 'farside'.
• Both sides of the moon experience night and day because moon spins about its own axis.
• Radio wave communication is becoming more popular, so it is important to note that the Farside is devoid of human interference in radio waves. So the Farside can have lunar radio observatories.

Birth of the Moon

• Several hypotheses were created to understand how the moon was born.
• Capture hypothesis, fission hypothesis, and co-formation hypothesis are among the three.
• These hypotheses were later discarded.

Apollo Missions

• The period between 1961 and 1972 was important to Moon’s study.
• NASA Apollo sent a series of missions to the moon.
• The missions sent lunar rock samples and provided insight into the moon’s nature.
• The Apollo missions collected about 381.7 kg of lunar samples.
• Soviet missions also brought back also brought back 0.321 kg of lunar samples to Earth.

Pre Apollo Hypotheses

• The capture hypothesis suggested that the Moon formed independently and was later captured by Earth's gravity.
• The fission hypothesis suggested Earth was spinning rapidly and became unstable, thus ejecting material that formed the moon.
• The co-formation hypothesis that Earth and Moon formed together from the solar system’s material.
• These hypotheses faced problems such as the capture hypothesis requiring a larger orbit and did not explain moon’s lower density and iron depletion. The fission hypothesis lacked sufficient angular momentum. The co formation could not explain Earth’s ratio similarities angular momentum.
• A successful theory will be one with geophysical, celestial and geochemical aspects.

Lunar Samples

• Lunar samples show differentiation, where denser material sank while lighter material rose.
• Analysis of lunar samples included the concept of isotopes in atoms.
• Isotopes are variants differing in neutron number, maintaining protons.
• Isotopic ratios are crucial in planetary science because they reveal various facts.
• Analysis revealed similarities in isotopic ratios meaning shared material origins between Earth and Moon.

The Giant Impact Theory

• The giant impact theory is the most accepted theory for the formation of the Moon.
• The early solar system experienced chaotic dynamics of colliding debris with impacts between bodies.
• The Earth and a Mars-sized rock, often referred to as Theia, collided about 4.5 billion years ago.
• Earth's metallic cores coalesced while ejected materials formed the proto-moon revolving around the Earth.

Evolution of the Moon

• Since its formation, the moon has undergone changes to its atmosphere.

Evolution of the Bulk Moon

• The impact hypothesis Moon molten state which formed the Lunar Magma Ocean (LMO) which lost heat, the loss of heat allowed low-density materials to buoyantly float, and heavier materials sink creating 'differentiation'.
• The upper crust became rich with minerals like plagioclase, while the mantle became rich in minerals like pyroxene and olivine.
• 80% of the LMO solidified in 1000 years, with solidification over tens of millions years.
• As the moon solidified, the surface density increased, leading to an overturn process where the solidified part sank and molten regions rose, resulting in mantle overturn.
• As a result of the mantle overturn, material sank.
• Various minerals crystallized due to varied chemical composition and pressure, potassium, rare earth elements and phosphorus.
• Moon’s samples from Apollo show basin formation from the Late Heavy Bombardment 3.8-4 gy ago.
• Cracks were formed on the surface by impacts, these became basalt rock.
• Basalts have different compositions depending on the Moon depths, basalts look like dark smooth regions called lunar Maria.
• Volcanic eruptions, seismic waves, surface changes and gravitational anomalies reflect international structures.
• The structure is a solid inner core with a ~160 km radius, fluid outer core to ~350 km, partial melt / lower mantle to ~587, mantle and a crust of 40-60 kilometers.
• Variations are evident in thickness across the picture due to impact events.
• A seismic discontinuity occurred at around ~560 km based on Apollo observations.
• Seismic waves differed compared to physical properties and chemical differences.
• As the presence of a partially molten region beneath about 1150 km, outer core molten is ~350 km. The core could be crystallized a solid inner core of ~260km.

Evolution of Moon's Atmosphere

• Today the Moon is known as an airless body.
• In the early days, the Moon's atmosphere was a couple hundred times ticker than Earth.

Timeline to the Evolution of Moon

• Epoch-I from 4.57 to 4.4 Giga years ago, atmospheric pressure was high by vapor abundance such as Silicon based materials.
• Epoch-II from 4.4 to 3.1 Giga years ago, frequent volcanism occurred.
• Epoch-III last 3.1 Ga till date, volcanism ceased larger impacts lessened and therefore the moon became airless.
• The moon has a “surface boundary exosphere”.
• Earth's exosphere begins at 550 km, while the Moon's exosphere begins right from its surface.
• Lunar neutral exosphere is a dynamic equilibrium between sink and source.
• Solar wind captures, thermal desorption and impact vaporization contribute to this lunar atmosphere.
• Solar wind capture occurs through hydrogen, helium and other ions.
• There is about 10^5 dayside cubic centimeters atoms, and 10^3 nightside.

Evolution of the Moon's Orbit

• The Moon’s orbit underwent a dramatic transformation and appeared 12 times larger than what is appears today.
• First life appeared 2000 million years ago, that is why the Moon has been formed long ago.
• The moon was 31 thousand kilometers away from the Earth whereas today geostationary satellites are 36 thousand kilometers away.
• The journey from 25 thousand to 4 lakh has been nonmonotonic, and today moon’s orbit is completely circular.
• The eccentricity is greater than but less than 1 for the ellipse .
• At time after the formation of the Moon, semi-axis was varied in distance.

Why Do Scientists Find Moon Interesting?

• The moon offers us potential for scientific study for humankind.
• Scientists have identified moon as the record-keeper, and can reveal early data on solar system.
• The moon offers a good reference for impact processes for planet scale, and studying the regolith.
• The goals include understanding the bombardment history of inner-solar system, providing information on lunar crustal rocks and the interaction of the solar wind, as well as the effects of the sun.

Successful Missions to Moon

• Categories of missions include orbiter missions, lander missions, rover mission.
• Luna-1 in 1959 was the first fly-away mission by USSR.
• Russia had the Luna and Zond lunar series and America had Ranger series.
• Luna-9 did the first lunar landing in 1966 as well as launched Luna-10.
• Surveyor was the first lunar lander series mission from US. US initated the Lunar orbiter series.
• Apollo-8 crewed the first mission to Moon, Apollo-10 followed, and Apollo-11 first lunar lander on June 20 1969.
• United Nations announced July 20 as international moon day.
• In 1970 the Russian Luna-16 retrieved samples.
• The United States demonstrated the first crewed rover on the lunar surface, in Apollo-15.
• In 1990, Japan, through its Hiten flyby/orbiter mission, resumed lunar expeditions.
• Japan is the first Asian country in lunar exploration.
• China later launched Chang'e-1 which had Asian contribution.
• India sent Chandrayaan-1 which carried an orbiter called Moon Impact Probe.
• Human made object sent to lunar study from Asia.
• Recent missions study the surface of esosphere of internal structures.

Moon Present Day

• Currently, the lunar missions have provided information on gravity anomalies and structure.
• Chandrayaan-2 was sent by India in 2019.
• The orbiting is studying the Moon while China’s Chang’e 5 has returned samples.
• Lunar missions the LRO, Chandrayaan-2, and Yutu-2 are currently active.

India's Missions to Moon

Indian Lunar Exploration Programme

• India's lunar mission began in 2008, Chandrayaan-1.
• The orbiter was used to examine the topography, minerals, elements and volatiles for water/ice signs.
• The Moon impact Probe MIP released in the polar region.
• Despite its short lifespan, Chandrayaan-I was a success.
• Chandrayaan-2 included an orbiter, lander / rover to track lunar mapping.
• Landing was prevented however, it is conducting remote and exosphere observations.

Future of India’s Lunar Missions

• The next in the series, Chandrayaan-3, will soft land in the high latitudes and will compliment Chandrayaan-2 with observations.
• The plan aims to study water or other volatiles at poles.

Chandrayaan-1

• HYSI (Hyper Spectral Imager) was used to do remote sensing.
• Chandra had 11 instrumentations from scientific institutions, an elegant example of international cooperation.
• Used imaging spectrometers as well as provided elements chemical for surface data.
• A radiation monitor provided data along with the energetic particle information in orbit.
• Carried moon impact probe MIP which had a radar altimeter as well as a quadrupole spectrometer.

Discoveries From Chandrayaan

• Moon in colour indicates water-ice in the lunar surface revealed through M3. This detected Hydroxyl radicals. Oh was associated to water-ice.
• Chandra’s Altitude Composition Explorer ChACE showed signs of water as they previously thought that. Moon used to be dry.
• Solar emissions from Sun are typically 400 km/s. SARA showed that protons scattering from ENAs.
• The C1XS on board can measure relative abundance like Mg, Al, Si, Ca, Ti and Fe, C1XS can measure Lunar rock. Evidence has unveiled about enhanced Sodium.
• SARA by SWIM showed that some of the physics was in the wake region. proton fluxes could be observed.
• Ar-40 which reveals that was the distribution at the MIP. Argon traces are in the upper crust due to radiant disintegration.

Lava Tubes on Moon

• The moon lacks intrinsic magnetic fields and atmosphere so vulnerable areas are impacted. Human settlement plans to tackle this with settlements on volcanic lava tubes that provide safe solutions and perspective for long work. Lava tubes form a high crust forms on the flowing lava beneath. Chandrayaan-I detected a lava tone with TMC’s.

Chandrayaan-2

• The 2009 Chandrayaan has prompted. India to propose a second lunar mission (Chandrayaan-2).
• With the use of an orbiter, the lunar terrain was discovered to have many scientific benefits.

Lessons from First Mission (Chandrayaan-1)

• C1XS follow up will use XSM to study rays from moons surface.
• CHACE-2 is studying exosphere

Chandrayaan-3

• CHACE-2 has an atomic mass measuring from 1-300 amu. The DFSR can also be used to analyze ionosphere of moon and 25 CM can also be used to take images or geological surfaces.

Chandrayaan In Operation

• Quality remote can in-situ with those payloads the data is being made public over 2800 public users.
• Research has yielded several insights to learn surfaces like that include water characteristics, craters with global argon distribution, as well as geofail dynamics.
• The dual frequency SAR is continuity to Chandrayaan with Enhancements with penetration at 5-10 meters to discover layers. This will provide insight on the craters.
• High results lead to a unique lunar surface with many folders with OHRCs.

Towards Chandrayaan-3

• Next in future Chandrayaan-3 is meant to soft land I latitudes. Rover an payload similar to that and will perform.
• The objectives are to study thermos, seismicity and the surface and will include landing, rover and proportion.

Indian Space Science Data Centre

• The data center is at ICDC, located at Byaulalu in K, hosting ISRO science, includes reduced and calibration data plus document for AstroSat.
• ISDA implements is with data and guidelines for scientists. Data is accessible at issdc.gov.in and for students.

Summary and Future Scope

• Moon provided collective data, to understand the surface and activity.
• Example water revolution on study the moon.
• Have helped to test existence of early solar.
• Testing models also help developing better to improve better understanding the formation of basins.
• They’ve also raised some questions such as the groundtruth, volatiles analysis.
• Far-side provides an attractive wave environment for astronomical results.
• Techs are also finding resource utilization for the creation. Technology development is underway for several civil.