Borderlands

British entering Baghdad on March 11, 1917

These are called the borderlands since the Middle East is in fact on the border between continents and cultures. Across these lands have passed many an army since ancient times. To the east is the heart of Asia. To the northwest are the nations of Europe. To the southwest is Africa. Whether 2,000 years ago or today, these lands seem to be the focus of much of the world's conflicts.

The nations and boundaries of today's Middle East are in major part (1) creations by the victorious European nations following the end of World War I and the breakup of the Ottoman Empire and (2) actions by the British relating to their former colonial possessions in India and North Africa. The resultant mess has created one great headache for the area's inhabitants and the rest of the world.

Nation Federations

The Middle East imagined here is primarily organized into four great federations of nations: Egyptian, Iranian, Semitic, and Turkic. The common thread uniting these federations is a language family. Two of the federations, Semitic and Egypt, have a common language, Arab, but are split for cultural, ethnic and geographic reasons. Ethnic groups within the federations having at least 10 million members (with some exceptions) are designated as distinct republics on the map.

Republics which may not fit easily into the four federations for historical reasons are imagined as Autonomous Nation States. The Kurd Autonomous Republic is one such instance. Israel and a smaller Lebanon are two others. Although it is possible in 200 years that these last two might be peaceably integrated into a Semitic Federation.

The rationale for the imagined nations and boundaries is covered in more detail below. 

Borderlands Map

I considered a map of a re-imagined Middle East in 2006 and dropped the project. I thought it might be too controversial. I also was unhappy with the topographic maps then available in the public domain for use as a base map.

The first issue of the Atlantic magazine of 2008 caused me to reconsider this post. It included an article entitled, "After Iraq", with a somewhat flippant map vision of a future Middle East. I thought, I could do better. I also discovered excellent topographic maps of the earth based on the data generated by NASA's Shuttle Radar Topography Mission satellite.

The map imagined below can be enlarged by clicking on it with the mouse. Any location on the map can then be brought further into view by clicking again on the desired location.

The boundaries of nations set forth on the map are based on a number of factors: current principal location of ethnic groups, consolidation of the sometime scattered locations of these groups, logical and/or defensible geographic formations (mountains, deserts, etc.) coterminous with the boundary, and political reality. For this to work, at least two mass movements of people would regrettably be required.

Three basins on the map (Caspian, Qattara, and Dead Sea) are shown filled with water to sea level.

Map base layer courtesy NASA, Shuttle Radar Topography Mission

Egypt

This federation is imagined as including peoples within the boundaries of present day Egypt and Sudan. The Darfur area and southern Sudan, home to primarily black African people, are seen as outside this federation, joining instead with more closely related groups in sub-Saharian Africa.

The below sea level Qattara Basin in northwestern Egypt is envisioned as being filled with ocean water with a channel connecting to the Mediterranean Sea. This new water basin would open an opportunity for a fishery and new cities along its shoreline. Most importantly, it would provide an alternative residence for the population outside the narrow corridor along the Nile River. Currently more than 90% of the inhabitants of Egypt and northern Sudan live along the Nile.

Iranian Federation

Present day Iran has a population of about 70 million. The imagined Iranian Federation is seen as including most of present day Iran, plus Afghanistan, Tajikistan and the western part of Pakistan. All of these regions are primarily inhabited by people speaking languages of the Iranian family, with about half of Afghanistan speaking Persian. Language speakers numbering 10 million or more are shown as separate republics on the map.

Three major groups inhabiting present day Iran are shown outside the Iranian Federation. These are the Azeri who speak a Turkish language and are also the principal inhabitants of Azerbaijan. They are shown in the Azeri Republic within the Turkic Federation. Another group is the Kurds, who are envisioned joining with their fellow Kurds from Iraq and Turkey in a Kurd Autonomous Republic. Last are the Arabs. Arab speaking western Khuzestan is seen as joining with Shiite inhabitants of southern Iraq in a new Mesopotamia Republic.

Kurd Autonomous Republic

The Kurds are seen as a special case in the Middle East. Numbering about 30 million, they are probably one of the largest ethnic groups in the world without their own country. As with many ethnic groups lacking recognized borders, they are scattered in many places in the area, with a large diaspora in western Europe. However, the main concentration of Kurds is in the region centered where Turkey, Iran and Iraq adjoin.

The imagined Kurd Autonomous Republic includes some but not all of these lands where the Kurds are most concentrated. Its northern boundary being Lake Van and the Hacres Mountains extending west, south of the Murat river. Kurdish regions of Turkey north of this line are excluded, as their inclusion would separate Turkey proper from its Turkic speaking cousins to the east in the Azeri Republic. A Turkic Federation split by a Kurd Republic would be impractical. Kurds ouside these boundaries that wanted to be part of the new republic would need to move within these boundaries.

The Kurd Republic would not be part of any federation, but is imagined as an autonomous entity under the direct oversight of the Solar Union.

Semitic Federation

The name recognizes that the language family historically dominate in this region was Semitic. Although the predominate semitic language currently is Arab, the Semitic name gives explicit recognition to other Semitic languages such as Hebrew. The boundaries within this federation are generally not based on ethnic differencies. The rationale for its organization is both the most complex and tentative of all the federations set forth here. Most of the designated republics within this federation do not exceed 10 million residents in population.

The nation of Iraq was created by the British at the breakup of the Ottoman Empire. The reimagined Middle East has the northern highlands becoming part of the Kurd Republic, with the rest divided among a new nation of Mesopotamia, a redesigned Iraq, and a new Baghdad city state.

Mesopotamia would include the primarily Shiite areas of Iraq south of Baghdad, Arab speaking western Khuzestan in Iran, and the primarily Shiite coastal area of Saudi Arabia north of Qatar, plus the island of Bahrain. The reconstituted Iraq would include the primarily Sunni Iraq north of Baghdad, western and southern Iraq beyond the Shiite areas and Kuwait, plus small eastern areas of Syria and Jordan. Kuwait, created by the British, is included since it is primarily Sunni Moslem in religion and would provide the new Iraq with its own outlet to the sea.

The Baghdad City State recognizes the Shia/Sunni divide of present day Iraq, with the country split between the two Moslem sects. Making the city a separate administrative entity would facilitate the creation of a more secular government open to equal opportunity for members of both sects. It also recognizes that division of the city between the two main Moslem sects would be an untenable solution. Baghdad, as the former capital of the Abbasid Caliphate, would be a prime candidate for the capital of the Semitic Federation.

The reimagined Syria would include most of current Syria plus southern Shiite Lebanon and the Golan Heights currently administered by Israel.

The new Palestine would include some of the West Bank portion of Palestinian lands, Jordan (with about 40% of its people being of Palestinian extraction) and the area of Saudi Arabia bordering the Gulf of Aqaba. Jordan, created by the British out of most of the post World War I Palestinian mandate to provide a kingdom for Abdullah of the Hashemite family, would be folded into a new Palestine. The area of present day Saudi Arabia along the Gulf of Aqaba would provide a new seaside home for relocated Palestinians of the Gaza Strip, a failed entity in its current isolated location and cramped size. The flat desert lands along the entrance of the Gulf would be watered by desalinated sea water to create farmland. The farmers, fishermen and rest of Gazan Palestine could live in peace in a greatly expanded homeland.

Hijaz would include some of the holiest sites of Islam; Mecca and Medina. This land would no longer be under the thrall of the intolerant and fundamentalist Wahhabi sect of Islam. Arabia would include much of the rest of today's Saudi Arabia plus the Arab Gulf states. The term "Saudi Arabia" would no longer apply. The boundaries of Yemen and Oman would be similar to today, with some minor expansion.

Last we come to Israel and Lebanon. The ideal situation would be their inclusion in a tolerant Semitic Federation. The alternative would be their existence as autonomous republics similar to the Kurds. The second situation would make the Arabian Federation a more likely name for this federation.

Turkic Federation

The Turkic Federation encompasses present day Turkey on the Anatolian Peninsula and a good part of the lands populated by Turkic language ethnic groups and formerly part of the defunct Soviet Union. The boundaries of the different Turkic language speaking members of this federation would generally be the same as today, with some minor adjustments to reflect ethnic realities and physical geography.

The Uzbek Republic is extended west into the much larger, but less populace, Kazahk Republic to give it an outlet on the Caspian Sea. The Azeri Republic has been expanded south to include Azeri areas of present day Iran. Slight adjustments of the borders of the Kazahk, Turkmen and Kyrgyz Republics reflect a desire to make them more logical and incorporate adjoining fellow members of their ethnic group. Some scattered members of these ethnic groups would need to move if they want to live in the same nation as the majority of their ethnicity.

Solaria and the Solar Union

The capital of the solar system should be located on the planet with the greatest concentration of population. As to its location on that planet, it should be in a region populated by people whose origin was primarily elsewhere and had not attempted to be earth's overlord. As a relatively new nation, Australia would not carry the cultural and provincial baggage of older civilizations. The Australia envisioned in 2200 would be home for races from throughout the earth, with Asians and Europeans predominating. 

Solaria

A great spaceport just outside the city would connect the city and earth to nations and communities established on natural and artificial bodies throughout the solar system. Subterranean tube trains would link Solaria with other Australian cities and sea ports connecting to the rest of the world. The city's newness and physical location, linked to the southern ocean and bordered by hundreds of miles of desert to the west, north and east, would facilitate Solaria's evolution over time as the capital city of the Solar System.

Solaria is envisioned as a new city located in the Lake Eyre region of the Australian desert which has been reformed using fusion or another massive energy source. Vast multi-use mega-structures would be located in the city center on a man-made island surrounded by a miles wide circular canal. Both parks and structures would overlook the circular canal. The circular canal would be connected to the ocean by a deep channel. This channel would cut through the desert landscape between the city and the Southern Ocean and be open to ocean going ships. The outside ring of the city would include structures climbing the geo-engineered mountain slopes and cliffs which surround the circular canal and which mountains were created from rock and soil removed as  the canal was dug.

Solar Union

The envisioned future community of Earth, its sister planets, asteroids and artificial habitations orbiting the sun must function within a political framework. The chart below presents a scenario of one sort of framework in which the envisioned society of 2200 might operate.

Sovereign members of this union would include national federations on earth, individual earth nations & city states and other individual and federations of planets, moons, asteroids and artificial structures in space. Directly dependent Solar Union territories would include space ports, research stations on earth and in space, significant wilderness areas, and frontier regions.

Political Structure

Solar System, Courtesy Wikipedia

The perceived political structure would support continued human progress both on earth and outer space in conjunction with the enhancement of the natural environment. The envisioned Solar Union would be a political union (similar to today's European Union) of independent political entities within the solar system who adhere to a common agreement or constitution.

The concept contemplates citizen representation through a Solar parliament. The parliament is envisioned as bicameral; with equal representation for political entities in one house and representation based on population in the other. There would be a prime minister elected by the two houses of the parliament. The supreme court members would be appointed for 10 year terms. The Academy of Sciences would be a new branch of government, recognizing the importance of science to the success of the Union.

Common Agreement

This Solar Union 'Common Agreement' would require: (1) functional democracy, (2) governmental authority exercised under a rule of law, (3) respect for human rights (happiness, religious, economic, environmental, social, health, education, political, etc.) and minority peoples, (4) support for free scientific inquiry, and (5) effective protection of the natural environment. Membership would be delayed for frontier human territories that are still being developed for habitation and denied to entities that fail to adhere to the common agreement.

 

Imaginary Places

These images are more than just imaginary futures or another dimension. They include actual places that can conjure up fascinating visions in the imagination. (Clockwise from upper left: Machu Picchu, Peru, Alicia Graham © 2005; Middle Earth from Tolkien's Lord of the Rings; Yangshuo, China, H Graem © 2007; The Moon Pandora from the movie Avatar)

Map of Tenoctitlan (Capital of the Aztec Empire) in the 1500s,
before it was destroyed by the Spanish

Herein can be visions that do not fit easily into the categories on this website. They are ideas or places that caught my fancy. They range from the fanciful to the practical. They may arise whole cloth from the imagination or be the ignored ideas of past visionaries that have fallen into history's dustbin. Some were actual places of which only the words or drawings of a lone chronicler remain. 

These visions have no relationship to current trends. The likelihood that they would become reality is slim, but the possibility is interesting. Given the sameness that can permeate our lives, imaginary places can transport one to a another realm for a while. Such visions may even stimulate enterprising souls to create future places that may actually transform at least a part of the world for the better.

Orion's Arm - A collective hard science fiction world building endeavor called Orion's Arm focuses on imaginary places, technologies and societies encompassing vast star systems and a timescale of 10,000+ years. Despite this seemingly unbounded character, the website is constrained by hard science, plausible technology and the requirement of realism in a number of realms.

Habitable Exomoons

Giant gas planet visible in the sky of a terraformed moon in the habitable zone
of an unknown star

Giant gas planets the size of Jupiter or larger have been found in orbit within a star's habitable zone. Although conditions on such gas planets would be adverse to any earth-like life, an orbiting moon comparable to earth's mass could exist and provide a more friendly environment.

Gas giants larger than Jupiter, with moons Earth-size or larger, are possible. Some researchers think the capacity to detect them—and even analyze them for habitability—may be just over the horizon. Earth-size moons could even form as planets and later be captured by a more massive gas planet's gravity to become a satellite.

NASA's successor to the Hubble Space Telescope, the James Webb Space Telescope (JWST), currently scheduled to launch in 2020, should open up the field of exomoons, assuming they are as abundant as theory predicts. It may even be able to resolve atmospheric constituents of those moons.

Moon habitability depends on a number of factors. Existence within the habitable zone is the first requirement, adequate size to hold a substantial atmosphere is another. A factor significant for the human experience would be the length of the day. The movie Avatar's moon Pandora could exist.

Moon Rotation and Tidal Forces

 

Giant gas planet and earth-size moon in the habitable zone, H Graem © 2008

In our Solar System, all the giant planets rotate about their axis in less than one earth day. Jupiter's day is less than 10 hours. A giant gas exoplanet orbiting in the habitable zone of a star of the sun's type would probably experience a rotation similar to that of our Solar System's giant gas planets. Moons orbiting this gas giant would be constrained by a number of different forces.

Where the moon is orbiting a giant planet the size of Saturn or larger, the moon's rotation will likely be restricted by its host planet. Based on our experience with moons orbiting the Solar System's giant planets, the moon will experience a tidal lock (similar to our moon with one side always facing the earth) by the planet. Other things being equal, a large moon will lock faster than a smaller moon at the same distance from the planet. Unless a moon is unusually distant from its host giant planet, it will be subject to this tidal lock.

The day of a moon tidally locked on its host planet will equal its time in orbit about the planet. The moons orbiting closest to the planet will have the fastest orbital speed and thus the shortest day. For most moons orbiting giant planets (except for those rare instances where there is no tidal lock), the length of the moon's day will be dependent on the orbital distance to the planet.

Using the four largest moons of our largest planet, Jupiter, as an example, the table to the left puts this situation in perspective. The moons are listed in the order of their orbital distance from Jupiter, the closest being Io. All four are tidally locked and thus rotate about their axis in the exact same time that they orbit Jupiter. Rounding off, their respective rotational times are 1.8, 3.6, 7.2, and 16.7 Earth days.

One concern with moons having orbital periods greater than 4 earth days is that the moon could be uninhabitable due to large swings in surface temperature between the day and night side. However, it is possible that even a modest amount of carbon dioxide in the moon's atmosphere would retain a tolerable temperature range despite having a day as long as several weeks. Clouds and large bodies of water should further moderate temperature extremes. 

If we want to find a moon with a day similar to that of earth, it will need to orbit very close to its host giant planet. In the case of Jupiter, Io comes closest with a rotational speed of less than two days. Tidal forces actively impact Io in ways beside its rotational speed, tidally induced heating of the moon's interior has created many large volcanoes which continually remake the moon's surface. 

Where the moon's orbit is circular, such propinquity results in a fixed tidal bulge on the side facing the planet. Where the orbit is more elliptical, the moon will approach and recede from the planet at regular intervals. The changing gravitational forces will result in a rhythmic compression or kneading of the moon's innards, generating a lot of heat. A moon close enough to the host planet to rotate in one day would experience significant volcanic and earthquake disruption as these powerful tidal forces heated its interior.

Roche Limit - Another limitation on very close moon orbits is the Roche limit, the closest distance an object can come to another object without being pulled apart by tidal forces. The Roche limit is the orbital distance at which a satellite will begin to be tidally torn apart by the body it is orbiting. 

If a planet and a satellite have identical densities, then the Roche limit is 2.446 times the radius of the planet. For Jupiter, the Roche limit for a moon the same density as Jupiter is 175,000 kilometers.

If the satellite is more than twice as dense as the host planet (as can easily be the case for a rocky moon orbiting a gas giant) then the Roche limit will be inside the host and hence not relevant. However, as we can see with Io, although the moon may survive at a distance equivalent to a day's rotational speed, its insides will certainly be shaken up by the tidal forces.

One scientist has proposed an interesting aspect of this heating associated with tidal forces. Tidal heating may substantially expand the outer habitable zone of a star when a large moon is involved.

Prospective Moon Life

Future hypothetical moon orbiting a gas giant planet located in the
primary star's habitable zone

A noteworthy aspect of life on these moons is that inhabitants of the moon's near side will always see the planet in their sky. The far side's inhabitants will never see it if they never travel away from that side. 

Variable daily tides also move across the moon due to the local sun, or suns, and other large moons. These fellow moons exert varying gravitational forces as their orbits bring them closer or further from our subject moon. As on Earth, oceans on the moon's surface would rise and fall in response to these latter tidal forces. 

An obvious difference from life on earth will be the frequency and length of solar eclipses. Given the size of the planet, inhabitants of a moon (those living on the near side facing the planet) should experience numerous and lengthy periods when the planet blocks their view of the sun. Eclipses will be most frequent when all three bodies, the primary star, host giant planet and the subject moon, are in the same orbital plane.

Given that large moons occur in groups among the gas giants in our Solar System, habitable moons could also occur in sets of two or more per planet. The prospect of two or more habitable, Earth-size moons in orbit around a giant super Jupiter certainly stimulates the imagination.

Other Factors Effecting Possible Habitable Moons

Habitability of extrasolar moons will depend on stellar and reflected planetary illumination of the moons as well as the effect of eclipses on their orbit-averaged surface illumination. Beyond that, with short day moons, tidal heating could increase surface temperature, effecting a moon's habitability.

The magnetic environment of exomoons, which is critically triggered by the intrinsic magnetic field of the host planet, has been identified as another factor of exomoon habitability. Most notably, it was found that moons at distances between about 5 and 20 planetary radii from a giant planet could be habitable from an illumination and tidal heating point of view, but still the planetary magnetosphere would critically influence their habitability.

Habitable Exoplanets

An imagined habitable exoplanet

Scientists are hot on the trail of habitable, earth-like planets. So what are such planets? They are places where human beings could live without any genetic manipulation. Higher forms of life characteristic of earth should thrive there. 

Habitability requires a planet large enough to maintain a gravitational hold on its atmosphere, yet not so large as to generate a crushing atmospheric pressure. Planetary gravity should not be so weak that our muscles and bones atrophy, yet not so strong that easy movement is impossible. 

Average temperature should result in liquid water as the normal state, with oceans on the planetary surface. Plate tectonics should assure a stable carbon concentration in the atmosphere, preventing a runaway increase in temperature. 

Large asteroids should not be constantly plunging through the atmosphere and striking the planetary surface. Radiation should not cause life to mutate incessantly, thus the need for a strong magnetic field to deflect the solar wind. The planet should not be tidally locked with its primary star such that one hemisphere always faces its sun and one is in perpetual darkness.

Reputable sources regarding habitable exoplanets include: Habitable Exoplanets Catalog, Habitable Zone Gallery, NASA and Planetary Biology, the latter with a sortable list of exoplanets, including habitable zone candidates.

 

Habitable Zone

 

Chart showing location of  a star's habitable zone depending on stellar mass and
radius of planetary orbit relative to earth's orbit of the sun

Habitable exoplanets need to orbit within a star's habitable zone, the region of space around a star where a planet would receive roughly the same energy as our Earth. This NASA site explains the formation of habitable planets.

The graphic to the left illustrates the variation in habitable zone around different star types. The graphic shows how both the distance of the habitable zone from the star and its width are directly dependent on the star's mass. The width of the habitable zone can also be affected by assumptions, such as cloud cover. 

Planets substantially larger than earth could harbor life. In fact, according to one article, such super earths - from about 2 to 10 Earth masses - may be superior at fostering life. 

The reader is cautioned that the definition of habitable zone differs among sources. For example, at the beginning of 2020, three sources presented widely different lists of planets in their respective habitable zone. These were (1) Habitable Exoplanets Catalog [55], (2) Planetary Biology [73], and (3) Habitable Zone Gallery [131].  NASA does not list potential habitable exoplanets.

The three lists emphasize different qualities of the subject planets and their respective stars. According to Habitable Exoplanets Catalog, sixteen (16) habitable zone planets were closest to earth (within 50 light years). According to Planetary Biology, forty (40) of its listed habitable planets orbited 'G' class suns similar to earth.

Super Earths; Gravity, Radius and Density 

An apparent disadvantage of super-earths, despite the expanded real estate, is the heavy gravity. All that additional planetary mass must be crushing.

Escaping the planet will be difficult, but super-earth gravity does not necessarily squash earthlike life forms. A remedy can be found in the planetary radius. A planet's surface gravity is determined by its mass divided by the radius squared [Gravity = M/R²]. Using that formula, a planet 9 times Earth's mass with a radius 3 times that of the Earth would have a surface gravity equal to Earth. On such a hypothetical super-earth, people would weigh the same as on Earth and have nine times the planetary surface to explore [Surface Area = 4 π x R²].

But wait, another problem now arises; the planet's density [Density = Mass/Volume = M/1.33πR³]. The density of water is 1 g/cm³. The planet Earth is 5.5 g/cm³. Our hypothetical exoplanet would have a density of 1.89 grams per cubic centimeter - closer to that of water than that of our Earth.

Internal structure of Titan, largest moon of Saturn, showing its  ice layers
Courtesy NASA

This density is virtually the same as Saturn's moon Titan. Titan is composed primarily of water. A super-earth of Titan's density and composition (located in the habitable zone with water in a liquid state) would likely be covered with an ocean well over a thousand kilometers deep. People may well explore its surface, but they will never find land upon which to settle.

Mars has a density (3.93 g/cm³) a little over 71% of Earth's. It also has an iron core which at super-earth size could generate a protective magnetic belt. Using Mars as our density model rather than Titan, we find a more satisfactory exoplanet. A hypothetical super-earth, with about 2.5 times Earth's mass and a radius about 1.54 times that planet, will have a density comparable to Mars. The surface area is almost 2.5 times that of Earth. At the same time, the surface gravity will be comparable to Earth.

Other super-earth options which achieve this earth surface gravity goal are possible. I will leave the calculations to others.

Habitable Zone and Eccentrics

Eccentric exoplanet passing through and outside its star's
habitable zone, Courtesy NASA-JPL Caltech

Certain eccentric planets whose orbit extends outside the habitable zone may nevertheless be habitable. While Earth and the other planets in our solar system travel around the sun in near-circular orbits, planets in other systems can have more comet-like orbits in which the distance from the planet to star varies. Such orbits, termed eccentric, would cause the planet to move in and out of the habitable zone.

The eccentric planet would move through the habitable zone and then further out into a long, cold winter. During this phase of the orbit, any liquid water on the planet will freeze at the surface; however, the possibility remains that life could, in theory, hibernate beneath the surface. These planets in eccentric orbits could still retain lifebearing properties depending upon the percentage of the total orbit which is spent within the Habitable Zone. This paper (a PDF is downloadable) describes the development of the habitable zone concept and its potential application to planets in extreme eccentric orbits. Another source discusses the influence of eccentricity on habitability.

Terrestrial Type

Habitability for life similar to that found on Earth requires more than just being in the habitable zone. To be habitable, the planet where life might exist should be of the terrestrial type. A terrestrial planet is primarily composed of silicate rocks and is not a gas giant. By the beginning of 2020, NASA counted 161 terrestrial planets orbiting other stars.

In contrast, NASA says scientists have discovered 1302 gas giants. Hot Jupiters, are defined as gas planets orbiting extremely close (orbit of less than 10 days) to their parent star. Hot Jupiters are the easiest extrasolar planets to detect via the radial-velocity method, because the oscillations they induce in their parent stars' motion are relatively large and rapid compared to those of other known types of planets.

These 21 exoplanets listed in 2020 are more likely to have a rocky
composition and maintain surface liquid water (i.e. 0.5 < Planet Radius
≤ 1.5 Earth radii or 0.1 < Planet Minimum Mass ≤ 5 Earth masses).
Planetary Habitability Laboratory, University of Puerto Rico at Arecibo

The Habitable Exoplanets Catalog [Click here to see most recent catalog] shows potential habitable exoplanets of the terrestrial type. They are compared with Earth and Mars using the Earth Similarity Index.

This index number is a measure of Earth-likeness, where Earth is the standard of comparison with an ESI value equal to one. Exoplanets with values above 0.8 could be considered Earth-like planets but those with values down to about 0.7 might still be habitable by microbial life.

The potential habitable exoplanets bear little resemblance to Earth. Most of the habitable planets circling dwarf stars are probably tidally locked with that star. The crushing gravity of some of the super-earths compared to Earth would result in the evolution of a higher level life form quite different from what we are familiar. The likelihood of a totally earth-like environment on any of the planets discovered so far is slim.

Need for a Moon? 

One matter of controversy respecting the existence of habitable terrestrial planets is the need for a large moon (such as Earth's moon) to stabilize the planet's obliquity (or axial tilt). An unstable obliquity could produce severe climate changes, potentially affecting the development of life. Many scientists theorized that the need for such a moon, and its expected rarity, made habitable planets less likely. A recent study concluded that the need for a moon to achieve such stability is over blown. This video of a SETI Talk presentation by Jack Lissauer goes into more detail regarding the newest thinking.

Extrasolar Planets

Moon containing life orbiting a giant gas planet within the habitable zone
of an unknown star. The image involves some artistic license. Gas giants orbiting
a sun-like star at distances similar to the Earth are likely to have clouds of water
ice, with white a characteristic color. These water clouds may be obscured
by higher layers of gas, primarily methane. Methane scatters blue light
weakly, so these deeper cloud regions will have a slight bluish tinge.

The first confirmed discovery of extrasolar planets (planets around another star - also called exoplanets) occured in 1992. Radio astronomers Aleksander Wolszczan and Dale Frail announced the discovery of planets around a pulsar. In 1995, Michel Mayor and Didier Queloz of the University of Geneva announced the first definitive detection of an exoplanet orbiting an ordinary main-sequence star (51 Pegasi). This discovery was made at the Observatoire de Haute-Provence and ushered in the modern era of exoplanetary discovery.

Discovery Methods

Technological advances allowed astronomers to detect exoplanets indirectly by determining their gravitational influence on the motion of their parent stars. The planets are usually discovered by measuring the change in Doppler shift of the star's light resulting from the star orbiting a common center of mass with a companion planet. The graphic to the left demonstrates this technique.

Several extrasolar planets were detected by observing the variation in a star's apparent luminosity as a planet passed or transited in front of it. The occasional transit of Venus across the sun is an example from our own Solar System. An hypothetical transit is illustrated on the right.

The European Extrasolar Planet Encyclopedia includes a number of observational programs managed out of Versoix in France near Geneva, Switzerland. According to the Encyclopaedia, 4232 exoplanets had been discovered by the end of 2020. At the same time, NASA's Exoplanet Archive counted 4141 exoplanets confirmed, with 5075 candidate planets. The Exoplanet Archive is operated by the California Institute of Technology under contract with NASA. The difference between the two databases highlights the uncertainties involved in exoplanet detection and confirmation.

Hot Jupiter

Most discovered planets are 'Gas Giants' or 'Hot Jupiters' (similar or larger in mass to Saturn or Jupiter) orbiting very close to their sun. Given the current early stage in planet searching technology, this preponderance of giant planet discoveries in close solar orbit should not be surprising. These would be the most noticeable planetary bodies given the weak degree of sensitivity of the available instruments.

As sensitivity increases in the future and new methodologies become common, the average range in planet distance from the parent star should increase and the average observed planet size should decrease. Astronomers have discovered that terrestrial planets might form around many, if not most, of the nearby sun-like stars in our galaxy.

Planet Searchers

Lick Observatory - Seeker of exoplanets - in a winter snow, H Graem © 2019

The Automated Planet Finder on the top of Mount Hamilton in the mountains east of San Jose, California is one of the newest and less expensive exoplanet searchers. The telescope will also be used to search for optical signals coming from laser transmissions from hypothetical extraterrestrial civilizations. Sponsored by SETI (search for extraterrestrial intelligence).

The newest searcher is TESS or Transiting Exoplanet Survey Satellite, an MIT-led NASA mission which is an all-sky survey for transiting exoplanets. TESS will monitor more than 200,000 stars for temporary drops in brightness caused by planetary transits. This first-ever spaceborne all-sky transit survey will identify planets of all sizes.The WASP or Wide Angle Search for Planets is an international consortium of several academic organisations performing an ultra-wide angle search for exoplanets using transit photometry. The array of robotic telescopes aims to survey the entire sky, simultaneously monitoring many thousands of stars.

Interstellar Travel

An obvious problem with finding exoplanets, including the holy grail of a planet habitable by human beings, is the current impossibility of interstellar travel, traveling to other stars. Some investigators are actively searching for ways to solve this problem.  Progress in revolutionary propulsion physics discusses interstellar methods currently being investigated.  Tau Zero Foundation examines the possibility of Interstellar Propulsion, giving a realistic overview of the situation and details specific efforts to find answers.

Mars

Future oceans on a terraformed Mars

Mars has been the subject of more speculation than any other planet in the Solar System. There is also a wealth of information on the web regarding all aspects of this planet. Rather than regurgitate what may have been better expressed elsewhere, the bottom of this web page points the way to the best of these resources. 

The focus of this Mars web page will be two topics of possible significance for Mars' future: caves and terraforming. Establishment of initial human bases on the planet will be greatly facilitated by the use of natural voids that may be remodeled for habitation. A permanent human presence requires some sort of terraforming of the planet. 

Tubes and Caves

On the terraformed globe image above, Arsia Mons is the last volcano to the southwest in the straight row of three. Olympus Mons, Mars' highest mountain, is the separate volcano to the northwest of the trio. The closeup to the right of the four volcanoes brings out greater detail.

The seven openings on the right were discovered on the slopes of Arsia Mons. A detailed scan of the martian surface could probably find a lot more such openings in volcanic regions of the planet. 

Evidence that the holes may be openings to cavernous spaces comes from the temperature differences detected from infrared images taken in the afternoon vs. the pre-dawn morning. "Whether these are just deep vertical shafts or openings into spacious caverns, they are entries to the subsurface of Mars," said co-author Tim Titus of the U.S. Geological Survey in Flagstaff. "Somewhere on Mars, caves might provide a protected niche for past or current life, or shelter for humans in the future."

Lava caves can be quite large. A closeup of one of the seven, 150 meters in diameter, clearly shows a vertical shaft. 

Openings to the Martian underground on the slopes of Arsia Mons

Gravity on Mars is about 38% that of Earth, allowing Martian lava tubes to be much larger in comparison. Lava caves (with surface irregularities removed) could provide sufficient space for Mars base activity after humans first land on the planet. They could provide an environment naturally sheltered from radiation and thermal extremes. Well designed entrances would keep out the Mars dust with its oxidants.

The Caves of Mars project has evaluated the feasibility of the use of caves for the initial human habitation of the planet. One approach to remodeling the caves for human habitation would be the "cured in place" technology used on earth to rehabilitate old drainage pipes. They are re-lined with a cooled, resin filled liner which hardens when heated. A similar approach could provide an air tight lining for Mars lava tubes or manmade tunnels. Unlined caves could serve as unpressurized hangars or garages. 

Once created, some sort of hardening would avoid any tube collapse, possibly a spray-on concrete-like substance made from available materials. A more porous insulating material also made in situ could then be applied. Air tight flexible lining or inflatable self-sealing fabric habitats could retain air. The habitat would be protected from solar radiation, micrometeorites, extreme temperature fluctuations (ambient temperature is believed to be stable in lava tubes), winds, and dust storms which could pose a threat to human health and technology. These natural shelters would also reduce the landed payload mass for manned missions which would be economically advantageous.^[1]

Terraforming

Hypothetical Terraformed Mars, Wikipedia

Beyond human missions to Mars in the next 25 years, what future can we expect on the red planet in 2200? Will man have altered the planet to create an environment more conducive to a successful human society, perhaps even enabling people to flourish? 

Regarding human alteration of the planet, Robert Zubrin and Christopher McKay have set forth the technological requirements for terraforming Mars. Modified Mars, an add-on to Google Mars by Frans Blok, is a detailed and vivid vision of such a future Mars.

Terraforming of Mars has been imagined or discussed on a number of websites. How Stuff Works proposes three methods to terraform Mars.  This National Academy of Sciences article proposes keeping Mars warm with new super greenhouse gases. 

One wonders if fiction, whether books or virtual worlds, can herald a future terraformed Mars reality? The Red, Green and Blue Mars trilogy is probably the most extensive literary effort to portray the eventual terraforming of the planet. The trilogy is a tale by Kim Stanley Robinson of the exploration and settlement of Mars--riven by both personal and ideological conflicts--in the early 21st century.

Image of a future Martian terraformed location beneath Olympus Mons from Modified Mars mentioned above

Other personal sites have been created to advance the concept of terraforming Mars. Martyn Fogg has created a website containing a compendium of studies regarding terraforming, primarily related to Mars. Mars Reborn is a portrait of a possible Mars one thousand years in the future. 

Martian Overview

An overview of what we know about the red planet can be found at Wikipedia. A NASA perspective on Mars has planetary facts and figures and a gallery of images of the planet. The ESA has a great portfolio of Martian images and videos. Marsnews.com provides current news articles respecting Mars.

Google Mars is the best place to start looking for maps of the Martian surface. It is comprehensive and provides an intuitive way to find various planetary features and information regarding their origin.  

Updated presentations of Martian scientific findings are provided by NASA's JPL. Other science findings (including maps and images) may be found at MOLA and Marsoweb, both NASA sites, and this ESA Mars Express scientific findings site.

Advocates of the human exploration of Mars include the Mars Society, MarsDrive, the Mars Foundation, Red Colony and the Mars Institute. A forum for Mars enthusiasts is provided by the Mars Society.