Global Heat Budget #3 – Ice

This is the third in a series of posts about the global heat budget. 

Ice is melting around the world. 

Greenland’s ice cap is melting.  Antarctica’s ice cap is melting.  Arctic sea ice is melting. Continental glaciers are melting.  Arctic permafrost is melting.  The melting is happening at a rate that is readily visible to people who live near natural ice.  From decade to decade and year-to-year, glaciers are visibly retreating, and can be directly verified by the most casual observer.   

Melting ice is the second most important heat sink on the planet, after the ocean (albeit a distant second).  Melting ice accounts for about 3% of anthropogenic heat retained in the atmosphere.  Melting ice is the second most significant proof that human-caused climate change is happening.  Melting ice may be the most significant consequence of climate change in terms of costs and damage to humanity. 

The data is unambiguous and irrefutable.  The volumes of melted ice have been measured by a variety of methods, including high accuracy satellite measurements.  The heat required to warm and melt this volume of ice can be calculated and compared to the heat trapped in the atmosphere by greenhouse gases, and the rising heat content of the oceans.  The volume of meltwater entering the ocean can also be compared to measurements of rising sea level.   The rate of sea level rise is already 3 times the rate of the past 7500 years, and accelerating.  The observed volumes of melting ice and the measurement of rising sea level provide unambiguous proof that climate change is real. 

Greenland

Ice on Greenland is melting.

Greenland covers an area one-fifth the size of Australia.  Almost all of Greenland is covered by ice, ranging between 1 and 2 miles of ice thick.  The Greenland Ice sheet contains more than 2.8 million cubic kilometers of ice.  That is enough to make sea level rise by 20 feet if it all melted.

NASA’s GRACE (Gravity Recovery and Climate Experiment) satellites have monitored the mass of the Greenland ice cap since 2002.  Gravity observations were supplemented by altimetry and radar data from overflights and satellites.  Other satellite observations include NASA’s early ICESat, and the ESA’s currently operating CryoSat2.

There is a strong seasonal signal in the history of ice loss from Greenland, with a slight build in ice mass during the Northern Hemisphere winter, and a stronger decline in the summer.  From 2002 to 2016, Greenland lost about 3900 gigatonnes of ice due to melting.  Each gigatonne is a little more than one cubic kilometer of ice by volume, and produces one cubic kilometer of fresh water when it melts.  Altimetry data show that most of the melting was concentrated near the coast, particularly on the western side.  Six feet to fourteen feet of ice has melted around the edges of the entire island. 

The GRACE satellite, designed for only a five-year life, actually worked for nearly fifteen years.  The last data was recorded in June 2017.  The replacement mission, GRACE Follow-On, is scheduled to be launched in five days, on May 19^th, 2018.  

NASA’s IceBridge is an airborne project using laser altimetry and ice-penetrating radar data to measure the elevation, snow cover, and total thickness of Greenland and Antarctic ice.  IceBridge will provide data to connect and calibrate data from the new GRACE satellites.   IceBridge was originally designed to replace data from the ICESat satellite, which failed after seven years of service.  ICESat-2 is planned to be launched in September, 2018, to replace ICESat.

Antarctica

Ice on Antarctica is melting.

Antarctica is about seventeen times larger than Greenland, and nearly twice as large as Australia.  Ice covers 98% of the continent, to an average thickness of over a mile.  Antarctica holds about ten times the volume of ice as Greenland.  If all of the ice on Antarctica melted (which would require centuries to occur), it would raise sea level by about 200’, placing most of the world’s major cities and human habitation under water. 

The GRACE data for Antarctica is noisier than the data for Greenland and shows a weaker seasonal cycle.  It seems likely that the melting season over Antarctica is not (yet) as profound as over Greenland. 

As with Greenland, the Antarctic ice sheet has been monitored by NASA’s Grace and ICESat satellites, and the IceBridge aerial observation program.  Earlier observations were integrated by the European Space Agency’s IMBIE (ice sheet mass balance comparison exercise) to provide the ice balance record from 1992 to 2010.  The chart showing both IMBIE data and GRACE data is shown below.  From 1994 through 2017, at least 2450 gigatonnes of ice on Antarctica melted.

I should note that gravity methods will not detect ice loss on the portions of the ice sheet that are floating (and more susceptible to ice loss).  Ice floating on water will have the same net density as ice-free water.  So, altimetry methods must be combined with gravity methods for a full determination of ice loss on Antarctica.  The East Antarctic (Filchner-Ronne) and West Antarctic (Ross) ice shelves are approximately 900,000 square kilometers in area.  Dozens of smaller ice shelves also exist.  The actual loss of ice from Antarctica may be greater than 2450 gigatonnes, because losses from these floating ice shelves are not detected by gravity. 

While melting of floating ice shelves is difficult to observe, it is also true that the melting of floating ice will not cause sea level to rise, at least as a first-order consequence.  The same buoyancy of ice shelves that makes sea-ice loss invisible to gravity detection means that sea level does not change when a volume of ice is converted to water.  Melting ice shelves matter to the earth’s heat budget, but not (directly) to sea level. 

The rate of future ice loss in Antarctica depends on feedback mechanisms.  The principle feedback mechanism is the restraining force that ice shelves exert on flowing glaciers.  Ice shelves impede the flow of ice from the continent and into the ocean; when those shelves melt, the rate of ice loss will accelerate.  The timing and amount of acceleration are unpredictable, so the best estimates of future sea level rise are uncertain on the high end.  We are fairly certain about the minimum expected sea level rise, but the maximum possible sea level rise is very uncertain.

Antarctic Sea Ice

For many years, Antarctic sea ice was not subject to the declines seen in Arctic sea ice (seen in the next section).  This was often referenced in commentaries on climate-change deniers’ web sites.  In recent years, Antarctic sea ice has declined, but it is likely to continue to show an irregular response to climate change.  The reason is simple.  Antarctic sea ice is regularly replenished by calving from Antarctic glaciers and ice shelves.  Anyone with tour-boat experience in Alaska knows that sea ice actually increases following calving events.  So, with a huge reservoir of ice in the Antarctic ice cap, Antarctic sea ice is likely to fluctuate, but not disappear, as the mother-lode of ice continues to flow and break apart, feeding the sea ice around the continent.

 Arctic Sea Ice

Arctic Sea Ice is melting.

In contrast to Antarctica, the Arctic has no mother-lode of ice feeding the polar sea ice.  The sea ice freezes and melts in a seasonal cycle.  For the past forty years, each cycle has ended with less ice, on average, than the previous cycle.  The loss of ice has accelerated over that period.   There was about 250,000 square miles less sea ice in the 1990s than during the 1980s.   From the 1990s to the 2000s, the decadal average showed a loss of about 500,000 square miles of sea ice.  The annual data from the current decade suggests an even greater rate of loss. 

Area is not the only measure of sea ice.  Some sea ice persists through multiple seasons, gaining thickness from season to season.  However, against the background rate of general melting, less and less ice persists from season to season, and the overall thickness of Arctic sea ice is also declining.   Between 1984 and 2016, 94% of the sea ice more than four years old had disappeared.

Image by M Tschudi and S. Stewart of the University of Colorado, and W. Meier and J. Stroeve of NSIDC.

Some researchers have attributed 30 percent to 50 percent of the loss of Arctic sea ice to natural variability, and 50 to 70 percent to anthropogenic influences, including direct warming by greenhouse gases, and the second-order influence of atmospheric circulation patterns. 

Overall, Arctic sea ice has declined by 12,000 cubic kilometers since 1980.   As noted in the section about Antarctica, there is no sea level impact due to the melting of floating ice, but there is an impact on the earth’s heat budget. 

The loss of sea ice in some of the peripheral seas of the Arctic Ocean (Chukchi Sea, Bering Sea, Barents Sea, and others) is more evident.  

Image Credit, Rick Thoman, National Weather Service, Fairbanks

Continental Glaciers

Continental glaciers are melting. 

People who live near glaciers are well aware of the historical and current melting of glaciers.  In Alaska and Western Canada, popular glaciers often have signposts or old photographs showing the earlier extent of the glaciers.  Some examples are the Columbia Ice Field in Alberta between Banff and Jasper National Parks, and in Alaska, Root Glacier near Kennecott mine, Exit Glacier near Seward, Portage Glacier and associated glaciers near Anchorage, and the many tidewater glaciers along the Alaskan coast, including Glacier Bay near Juneau, College Fjord near Valdez, the glaciers of Kenai Fjords National Park, and Columbia Glacier near Valdez.  Glaciers are in retreat, on a scale which is noticeable from year to year and dramatic over the course of decades. 

The UN Glacier Monitoring Service and its predecessor organizations have measured the melting of continental glaciers, other than Greenland & Antarctica.  WGMS issued major reports in 2008 and 2015; each report shows overwhelming evidence of melting of glaciers worldwide.  WGMS includes data on about 100,000 glaciers, with digital outlines of about 62,000 glaciers; data on glacier fluctuation includes over 35,000 length observations for nearly 2000 glaciers (as of 2008).  Detailed mass balance observations are conducted on a smaller number of reference glaciers (including the most volumetrically significant glaciers).  Data from reference glaciers are extrapolated to other glaciers on the basis of regional association, altitude and latitude.

At any given time, a small number of glaciers are growing, due to natural fluctuations of snowfall, warmth, and air circulation. But the great majority of glaciers worldwide are melting. 

Annoyingly, the WGMS does not report summary ice loss in terms of cubic kilometers or gigatonnes.  Glacial Mass Balance is reported in terms of meters of water equivalent, a vertical measure of average ice melted.  Volumes of melted ice can be calculated from the reported total area of glaciers under study.  Those volumes can then be used for purposes of understanding the global heat budget and sea level rise. 

Sea Level

The earth entered a period of cyclic ice ages about 3 million years ago.  The last 600,000 years have been characterized by ice age cycles of about 100,000 years, apparently triggered by variations in earth’s orbit.  The influence of the orbital cycles is enhanced by feedback mechanisms, including CO2 and the reflectivity of ice.  The peak of the last glacial cycle occurred only about 20,000 years ago, and remnants of ice may have persisted in Ontario until about 8,000 years ago.

Deglaciation following the last ice age was mostly complete by 8000 years ago.  We know this from studies of sea level and sediment cores.  Sea level rose by about 80 meters between 14,000 years ago and 8000 years ago, an average rate of 1.3 cm/year.  From 7500 years ago to the 20^th century, sea level rose only 5 meters, a rate of 0.07 cm/year.   Through the 20^th century, sea level rose at about 0.2 cm/year, a significant increase over the background rate.  Satellite data over the past 25 years shows that sea level rise has accelerated to 0.35 cm/year, five times the rate of sea level rise for the past 7500 years.  This is a clear indication that global warming from human greenhouse gases is contributing to melting ice.

Additional heat retained by greenhouse gases will result in a faster rate of melting ice, and higher sea level rise.  Current forecasts of sea level rise range from about 2 feet to 8 feet by the end of the century.  Sea level rise of only 4 to 6 feet would seriously damage some coastal communities around the world, including the inundation of barrier island and low-island communities.

Heat Budget

From 2003 to 2016, greenhouse gases retained 1.6 x 10²³ joules of heat in the atmosphere, according to tables of radiative forcing published by NOAA (https://esrl.noaa.gov/gmd/aggi/aggi.html).  This figure for anthropogenic heat does not include the effect of cooling or warming aerosols, primary heat from fossil fuels and deforestation, or other minor sources of heat.  Estimates for some of these other anthropogenic disturbances are found in the IPCC 5 report, but only through the year 2011.

We have good estimates of the cumulative ice lost from Antarctica, Greenland, Arctic sea-ice and Continental Glaciers from 2003 to 2016, due to high-quality satellite observations.  About 10,400 gigatonnes of ice was lost over that period.  The heat required to warm (+10 C) and melt that volume of ice is 3.7 x 10²¹ joules, or about 2.3% of the total heat retained by greenhouse gases.  The allocation of heat to warm the ice by 10 degrees C was to reflect heating of an equivalent amount of ice, which has not yet melted.  Average temperatures of -10 C from core-holes in Greenland and Antarctica were taken as the ambient temperature of ice before melting. 

Considering that about 2.9% of the earth’s surface is covered by ice, this seems like a reasonable distribution of greenhouse heat which is going to warm and melt ice.  Looking forward, if a higher percentage of heat goes towards melting ice, sea level will necessarily rise faster.  Possible reasons for faster melting of ice could be more rapid ice flow from Antarctica and Greenland.  This might occur as the base of the ice is lubricated by meltwater, or when restraining ice shelves are lost around Antarctica.

References

Antarctica and Greenland

NASA GRACE Ice Mass, Antarctica and Greenland

https://climate.nasa.gov/vital-signs/ice-sheets/

Grace Data

Wiese, D. N., D.-N. Yuan, C. Boening, F. W. Landerer, and M. M. Watkins (2017) Antarctica Mass Variability Time Series Version 1 from JPL GRACE Mascon CRI Filtered. Ver. 1, PO.DAAC, CA, USA. Dataset accessed [2017-06-07] at http://dx.doi.org/10.5067/TEMSC-ANTS1

IMBIE:  Ice Sheet Mass Balance Inter-Comparison Exercise

Integrated Methods Measuring Ice Mass

http://imbie.org/

Arctic Sea Ice

Arctic Sea Ice Volume

http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly/

Chart with relative volume loss (km3) to 1980. 

https://www.ncdc.noaa.gov/snow-and-ice/extent/sea-ice/N/1

Charts of Arctic Sea Ice Extent by Month

https://nsidc.org/arcticseaicenews/2018/05/arctic-winter-warms-up-to-a-low-summer-ice-season/

Image of declining multi-year Arctic Sea Ice.  Image by M Tschudi and S. Stewart of the University of Colorado, and W. Meier and J. Stroeve of NSIDC.

http://earthsky.org/earth/decline-of-arctics-thickest-sea-ice

Arctic Sea Ice

Multi-year ice grows up to 4 meters thick, while single-year ice is 2 meters thick at most.

http://www.hindustantimes.com/world-news/climate-change-arctic-lost-nearly-95-of-its-old-ice-since-1984/story-XJiOVQT3bMeqN4NVrz67KJ.html

the area covered by Arctic sea ice at least four years old has decreased from 1,860,000 square kilometres in September 1984 to 110,000 square kilometres in September 2016.

Continental Glaciers

http://wgms.ch/downloads/WGMS_GGCB_01.pdf

World Glacier Monitoring Service bi-annual update, 2015

http://www.the-cryosphere.net/7/141/2013/tc-7-141-2013.pdf

Volume estimate for Glaciers and Ice sheets (other than Antarctica and Greenland.

Asteroid 16-Psyche, Crown Jewel of the Solar System

Psyche is a special asteroid.   It is the crown jewel of the Solar System, the literal heart of the asteroid belt.  Psyche is the only known pure iron-nickel asteroid, presumably the core of a former planet, ancestor to many of the asteroids.  Without question, Psyche is the largest source of workable metal in space, and is therefore the key to mankind’s future expansion in space.  The world’s space agencies should recognize the unique potential of this asteroid, and expect competition between nations and companies for this critical resource.  Action by the UN may be necessary to establish rules for fair sharing of the resources on Psyche.

Iron from Psyche may be essential to constructing an artificial magnetosphere over Mars.  An artificial magnetic field is believed necessary to re-establish the Martian atmosphere, liquid water, and warmth to make Mars suitable for human habitation.

Artist's conception of Psyche, with orbiter spacecraft.

Image Credit NASA

The Heart of the Asteroid Belt

The asteroid belt lies between the orbits of Mars and Jupiter, at a distance from the sun of 2.2 to 3.2 astronomical units (au), where an astronomical unit is the distance of the earth from the sun.  The belt is actually a set of three belts of objects, with narrow divisions between them.   Asteroids are widely spaced, at an average distance of about 600,000 miles, or about 2.4 times the distance from the earth to the moon.  Scenes of densely clustered colliding rocks in science fiction movies are not accurate depictions of an asteroid belt, at least in our solar system.   (But we have not yet been to the Hoth system of the Star Wars universe.)  Evidence from meteorites suggests that asteroids are the remnants of one or more proto-planets formed in the earliest days of the solar system.  The planet which originally contained Psyche broke apart for unknown reasons, perhaps due to a collision with another planetary body.  Jupiter’s gravity plays a role in keeping the asteroids from re-assembling into a planet. 

Image Credit: Karl Tate, Space.com

Formation of an Iron-Nickel Core

The meteorites we find on earth are a rock collection telling the story of the solar system.  Many meteors were thrown into space by collisions between comets, asteroids, and planets.  After untold years circling the sun some of them fall to earth.  Scientists have found meteorites from the moon and from Mars.  Some meteorites are composed of the primordial material of the solar system, and some represent a cross-section through a planet like earth.  There are meteorites which contain the common minerals which compose the earth’s mantle -- olivine and pyroxene.  Then, there are other meteorites which are made of iron and nickel, the materials which compose the earth’s core.  In the early days of geology, the composition of meteorites was a strong hint to geologists about the structure and mineral composition of the deep earth. 

A rocky planet is formed by the agglomeration of debris in space, through mutual gravitational attraction.  As the adolescent planet grows through accretion, the falling debris add heat, producing a partially or completely molten planet.  The abundant heavy metals, iron and nickel, coalesce in droplets and sink to the center, forming the metallic core.  The differentiation of a planet into the rocky mantle and metallic core implies a melting history, and enough mass for gravitational separation of iron and nickel. 

3D Model of Psyche

Image Credit: Josef Ďurech, Vojtěch Sidorin, Astronomical Institute of the Charles University

Mineralogy of the Core

Iron-Nickel meteorites give us our only direct look at a planetary core.  These meteorites originated from the disintegration of early planets, or from the object which collided with earth to produce the earth’s moon.  These meteorites are predominantly iron, alloyed with 5% to 25% nickel.  The typical mineral texture is octahedrite, which is a laminated composite of iron/nickel alloys kamacite and taenite.  The laminated structure forms by exsolution of the alloys during crystallization, and is known as the Widmanstatten pattern.   The pattern is quite beautiful, and individual crystals are often several centimeters to tens of centimeters in size.  Widmanstatten pattern in iron-nickel crystals grow slowly, and such crystal sizes imply slow cooling (millions of years) within a planetary body of considerable size. 
[I first saw the interior of an iron-nickel meteorite in the hallway display case in the geology building at Indiana University.  I noticed the extremely large crystals for an igneous rock, and immediately realized that it must have formed in the deep interior of a planet. Also, the separation of iron & nickel from silicate minerals implied a planet-wide melting event, with gravity segregation of the heavy metals.]

Octahedrite, with Widmanstatten texture

Psyche

The asteroid Psyche is the only known asteroid with the reflective properties (albedo) and density of iron-nickel.  The density of Psyche is estimated according to its size and gravitational influence on neighboring asteroids.

The mean diameter of Psyche is about 180 to 200 km, with a mass of 2.3 x 1019 kg, or 23,000,000 billion metric tonnes.  That’s a lot of iron. 

The name Psyche is drawn from Greek mythology, for a mortal woman who married Cupid (Eros) and was granted immortality.  The asteroid Psyche was the sixteenth asteroid to be given a symbol, and is therefore sometimes known as 16-Psyche.  The symbol is an inverted semicircle, representing a butterfly wing (a symbol of innocence from Renaissance paintings), with a star above it.  [in this post I have dropped the irrelevant “16” in the asteroid name.]

Psyche and Eros, Francois Gerard, 1798

Costs to Earth Orbit

The cost to launch material from earth to space is high.  Using the United States’ space shuttle, the cost to launch one kilogram to low earth orbit (LEO) was $22,000.  When the fleet of space shuttles was retired following two disasters, the cost rose to $33,000/kg.  Costs are now falling rapidly, thanks to intense innovation and competition from private companies, such as SpaceX and Blue Origin.  SpaceX’s newest Falcon 9 will launch payloads to LEO for $4100/kg, and the planned Falcon Heavy rocket will bring costs down to $2200/kg.  Higher orbits are necessarily more expensive, typically double the cost of low earth orbit.

The International Space Station has a mass of 419,455.  Most of the station was built during the time that costs were greater than $20,000 per kg.  If we were to rebuild the station, using the expected costs of the Falcon Heavy rocket, the costs of launching the material would be just under one billion dollars.  But suppose we wanted to build something big?  Let's take a large cruise ship, capable of carrying 1000 passengers, as an example.  The Crystal Serenity has a mass of 68,870 gross tons, or 62.6 million kilograms.  The cost to launch the material to rebuild the Serenity in orbit would be about 138 billion dollars.  Just think how much cheaper and easier it would be if the material to build things was already in space!

In short, launching stuff from earth to space is insanely expensive.  To build anything large in space, we must make use of materials that are already in space, and preferably already smelted by nature into metal.   In short, we need Psyche.  

Image Credit: Greybox.com

What We Will Do

Novelist Neal Stephenson wrote a detailed description of what could be done with a metallic planetary core in his novel “Seven Eves”.  In Stephenson’s novel, the moon has improbably disintegrated, providing the metallic core which will give humankind (or rather, womankind) the means to build a society in space.  Setting aside the improbability of Stephenson’s plot, his account gives a clear idea of the value of the asteroid Psyche. 

Cheap, abundant energy is necessary for exploitation of Psyche.  Today’s technical options would be a nuclear fission reactor or giant solar panels.  It is possible that fusion technology may be available in time to provide energy for the project. 

Initially, Psyche will be mined.  Pieces small enough to be moved will be cut from the asteroid, and sent into lower solar orbit.  The orbital velocity of Psyche is about 17 km/sec.  I admit that I don’t know the delta V or energy required to drop a ton of iron from Psyche to earth’s orbit, but I believe it is possible.  A magnetic accelerator or rail gun could launch the packets of iron from the asteroid, adjusting the orbit to deliver the packets toward earth.  A nuclear reactor (or perhaps fusion reactor) would provide electricity for the rail gun.  Energy could be stored in a large capacitor or set of capacitors until needed for launch.  Conditions are perfect for building such a capacitor – there is vacuum and lots of iron.    At the receiving end, the packets of iron would be captured using a gravitational assist from the earth and moon, and set into an orbit for construction purposes. 

Subsequently, the interior of the asteroid will then become a place of habitation, perhaps the first sustaining human colony in space.  The exterior of the asteroid will shield the colony from radiation, and spinning the asteroid can provide artificial gravity, thus solving two of the most damaging aspects of long-term survival in space.  In the long term, the capture of a comet or ice-bearing asteroid would give the colony much of the physical material necessary for sustainability.

Current Plans

NASA is now planning a mission to Psyche.  The spacecraft will be an unmanned probe that will orbit Psyche.  Instrumentation planned for the probe appears fairly basic, providing for imaging and basic mineralogic identification, including ice, if it exists.  Propulsion would be by a relatively low-power solar-electric engine, probably an ion-drive.   NASA says that the probe will be launched in 2023, and will not arrive at Psyche until 2030 (although there is a 2-year discrepancy in the indicated transit time and arrival date in the official announcement).  

International law governing the commercial use of asteroids was established in 1967, in the Outer Space Treaty signed by 98 nations.  Three updates to the treaty were signed in the late 1960s and 1970s.  The treaty prohibits any territorial claims, but allows mineral extraction.  Of course, the treaty does not address how programs competing for the same resources would be adjudicated, or how interference between programs would be resolved.  It is likely that primacy would be an important factor in any dispute over access to Psyche’s resources.

At least three well-funded companies and a government-led effort in Luxembourg are specifically interested in asteroid mining.  In addition, there are a number of private companies developing technologies and actively seeking profit in space.  These companies must surely be considering plans for the exploration and development of the resources on Psyche.

In my opinion, NASA’s schedule for the mission to Psyche is far too slow.  I am not the only person to realize that Psyche represents a unique commercial opportunity, and development opportunity for mankind.  If NASA continues on the proposed schedule, they may be late to the party.   NASA may find that private companies and foreign governments have already placed their flags on Psyche.  These other parties may be well ahead of the United States in developing plans for the exploitation of the asteroid.

Mars

Within the past year, NASA’s MAVEN Mars orbiter proved that the solar wind stripped away Mars’ atmosphere, leading to the frozen world that exists today.  In Mars’ earliest history, it had a magnetic field that protected the atmosphere from the solar wind, as earth’s magnetic field now protects earth’s atmosphere.  That magnetic field died long ago.  When the atmosphere was blown away, the temperature plummeted, the water froze, and the planet became a frozen, barren world.

Scientists at NASA recently proposed an audacious plan for restoring atmosphere, warmth and water to Mars.   Scientist Jim Green proposed putting an artificial magnet in between Mars and the Sun, stationed permanently at the L1 (LaGrange 1) position, where gravity from the Sun and Mars are perfectly balanced.  A magnetic field large enough and strong enough would shield the planet, allowing the atmosphere to naturally recover.  Initially, atmosphere would accumulate from volcanic emissions.  After some atmosphere had accumulated, the Martian icecaps would sublimate and melt, releasing carbon dioxide and water.  Atmospheric pressure is expected to recover to about half of the pressure of earth’s atmosphere at sea level (equivalent to about 15,000’ of elevation on earth).  The scientists believe that Mars’ atmosphere and liquid water could be restored within 100 years.  Converting CO2 to breathable oxygen would take somewhat longer. 

Image Credit: NASA

But how would you build an electromagnet large enough to protect a planet?
You would need a lot of conductive metal, and a magnetic core….

Clearly, the asteroid Psyche could be essential to the idea of terraforming Mars by building an artificial magnetosphere.  Psyche is the only readily available source of sufficient metal to build such a magnet.  Which gives even more urgency to the exploration of Psyche, the crown jewel of the Solar System.

References

Meteorites

https://www.pibburns.com/catastro/meteors.htm

http://geology.com/meteorites/meteorite-types-and-classification.shtml

Launch Costs

http://space.stackexchange.com/questions/2015/what-is-the-current-cost-per-kg-to-send-something-into-gso-geo

http://www.businessinsider.com/spacex-rocket-cargo-price-by-weight-2016-6/#bottle-of-water-9100-to-43180-1

http://space.stackexchange.com/questions/1989/what-is-the-current-cost-per-pound-to-send-something-into-leo

Image credit

http://starfrontiers.wikia.com/wiki/Ship_Construction_Centers

NASA Psyche Mission

http://www.hou.usra.edu/meetings/V2050/pdf/8250.pdf

A FUTURE MARS ENVIRONMENT FOR SCIENCE AND EXPLORATION. J. L. Green1, J. Hollingsworth2, D. Brain3, V. Airapetian4, A. Glocer4, A. Pulkkinen4, C. Dong5 and R. Bamford6 (1NASA HQ, 2ARC, 3U of Colorado, 4GSFC, 5Princeton University, 6Rutherford Appleton Laboratory)

https://www.nasa.gov/press-release/nasa-selects-two-missions-to-explore-the-early-solar-system

https://www.jpl.nasa.gov/missions/psyche/

https://en.wikipedia.org/wiki/Psyche_(spacecraft)

Asteroid Mining

http://www.planetaryresources.com/#home-intro

Planetary Resources.   Company is financed by a bevy of billionaires.    Backers include Larry Page, Eric Schmidt, Ross Perot, James Cameron, Charles Simonyi and K Ram Shiram. 

http://www.kesellc.com/

Kepler Energy and Space Engineering

http://deepspaceindustries.com/

Deep Space Industries

Science Fiction Inspiration
Neal Stephenson, 2015, SevenEves, 880p.
Stephenson's plot involves survivors of global disaster building a sustaining colony in a metallic planetary core.

Robert Heinlein, 1966, The Moon is a Harsh Mistress, 382p.
Heinlein uses magnetic accelerators to launch cargo capsules from the Moon to the Earth.

Harold Goodwin, 1952, Rip Foster Rides the Grey Planet, 250p.
A cold-war youth novel about international struggle for control of a unique asteroid made of Thorium.

And here are a couple more space art images, because they are cool.

On Human Opportunity

There is a small theater for visitors at the NASA Space Center in Houston, called "Destiny Theater". Every hour, every day, they show a film there called “On Human Destiny”.  This beautiful and deeply moving film documents the history of space exploration, using striking historical film footage.  The film concludes that it is our human destiny to explore space and colonize other star systems. 

I don’t believe in human destiny.  I believe in human opportunity.

There is no force which predetermined that humans should reach space, spread life to other star systems, or colonize other planets.  There is only our human potential to do so.  Whether we succeed in becoming something more than we are today or become a geological footnote in the history of a small planet depends on us.  It depends on our choices and our ability to cooperate.  It depends on our ability to work.  It depends on our ability to solve problems.   It depends on what we choose to do.  It depends on us.

Rarity of Human Life

In the history of the world, or the history of the galaxy, the evolution of the human species is an incredibly rare and improbable event.  Even given our debut as a tool-making genus about 3 million years ago, and a species capable of abstract thought 70,000 years ago, our technological civilization is an additionally unlikely and very recent development.   Against all odds, we stand on the cusp of meaningful space travel; we stand on the cusp of interstellar transmission of life.

The universe is about 13.8 billion years old.  By comparison, we have had the ability to communicate by radio broadcast for 122 years.  That is 0.0000000088^th of the lifetime of the universe.  Or consider our planet, which has existed for 4.6 billion years.  We have had the ability to communicate by radio for a fraction of 0.00000003 times the life of our planet.  Putting it another way, if aliens had randomly looked our planet at any time during the life of the planet to date, they would have had a 0.00000003th  chance of noticing that there was an intelligent species, capable of radio communication.  [Or, at least a species capable of communication, with the question of intelligence unresolved.]

Rarity of Intelligent Life in the Galaxy

The Drake Equation, formulated in 1961, describes the probability that a civilization capable of radio communication exists in the galaxy at the present time.  Many variables in the equation are poorly constrained (obviously).  But astronomical knowledge is rapidly reducing the uncertainty about the number of habitable planets in the galaxy.  The principal remaining uncertainty is the expected lifetime of a technological civilization, as pointed out by astronomers Carl Sagan and I. S. Shlovski in 1966.

The equation begins with a large number representing the number of stars in the galaxy, or the rate of star formation in the galaxy.  Factors representing some fraction of those stars successively pare down the number of potential civilizations, according to necessary criteria for life, for intelligence, for technology, and for longevity of the civilization.  The equation looks like this (from Wikipedia):

 N = R_* ^. f_p ^.n_e ^. f_l ^. f_i ^. f_c ^. L

where:

N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);

and

R* = the average rate of star formation in our galaxy

fp = the fraction of those stars that have planets

ne = the average number of planets that can potentially support life per star that has planets

fl = the fraction of planets that could support life that actually develop life at some point

fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)

fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L = the length of time for which such civilizations release detectable signals into space

Some variants of the equation use the total number of stars in the Milky Way as a starting point, rather than the rate of star formation   That number is between 200,000,000,000 and 400,000,000,000.

Here are my guesses for these factors. 

My Assumptions for the Drake Equation:

80% of stars have planets.

20% of planetary systems have at least one habitable planet

20% of habitable planets develop life

1% of planets with life develop intelligence

20% of planets with intelligence develop radio technology.

The average lifetime of a radio-capable technological civilization is 2000 years. 

These assumptions yield an estimate that there is one technological civilization in the galaxy at the present time – us.  If I adjust the factors such that there are 2 civilizations in the galaxy, the average distance to another civilization would be about 35,000 light-years.  Thus the time required to communicate with another civilization would far exceed my estimate for the expected lifetime of a civilization. 

There are a number of interactive calculators for the Drake Equation available on the Internet.

Human Opportunity

“The Earth is just too small and fragile a basket for the human race to keep all its eggs in.”                                              Robert Heinlein

Against incredible odds, humanity stands on the cusp of interplanetary travel.  Some of the world’s best and brightest people are seriously making plans to colonize Mars.  And if the other planets in the solar system are too inhospitable to support an independent human civilization, scientists have discovered a thousand planets around other stars – and these are but a tiny fraction of the number that must exist. 

Still, I am reminded of the title of a 1973 book by Ben Bova: Starflight and other Improbabilities.  As we understand physics today, the speed of light is an unyielding limit.    Voyages to the stars would require generations to complete the voyage and consume vast resources.  The probability of success for any particular venture would be slim.  But the tantalizing possibility of interstellar colonization is possibly, just barely within our grasp.  A program to gain more information about other planets is the first step.

I can imagine launching miniaturized microprobes, using magnetic accelerators in space to catapult them near light speed.  Returning the data to earth is problematic; but perhaps the probes themselves could use the gravity of stars to reverse course to earth.  Alternatively, a series of relay craft, with deployable antennae could follow the probe and transmit the data back to earth. 

And if colonization of the stars proves to be impossible, we could at least do what life does: propagate itself.  We could send seed packages to other star systems which would spread the miracle of life to other worlds.  If that alone is humanity’s legacy, it would be a worthy monument that we lived, developed science and technology, and gave life a new chance on barren worlds.

If life exist on other planets (as I expect it will on some, in a simple form) we should respect and preserve that life.  But I would not let protection of speculative simple life prevent our own further development.  Earthly life has proven its ability to develop complex forms, ecosystems, intelligence and technology, and I value those more than non-sentient algae.  We do not yet know what we might achieve, but today, we appear to have achieved more than any other life in the galaxy.  We owe it to those who have gone before to reach for what more we can become.

That is the opportunity for humanity.

What We Must Do: A Short List

Colonization of the stars, by people or earthly life, will not happen by itself.  Realization of this opportunity will only happen if people actively work toward that goal, through deliberate, directed effort and management of problems facing humanity on Earth. 

You may have noticed that I highlighted the final parameter of the Drake Equation – the expected lifetime of a technological civilization.  My guess is that a technological civilization will exist for about 2000 years before self-destructing due to environmental collapse, war or other strife.  Clearly, the longer a civilization can last, the better the chances of realizing Human Opportunity.  Therefore, our first goal is to ensure the longevity of civilization for our descendants.

Here is a short list of what we must do to realize our very rare, improbable human opportunity.

1)      Bring peace to the globe. 

Nationalism was the great sin of the 20^th century, causing two world wars and countless smaller conflicts.  In the 21^st century, nationalism is still rampant, even resurgent in the first two decades of the new millennium.  Our job in the next century should be to render national borders obsolete, uniting economic interests and blurring national identity until war between nations becomes a ridiculous idea.  Global spending on the military is about 2.3% of GDP; spending on all space products and services is about 0.4% of GDP, or about 1/5 of the spending on defense.  Just imagine what we could accomplish if that ratio was reversed!

Religious conflicts also need to come to an end.  Over 3000 distinct religious sects exist on Earth, generally with each one claiming to be the single true faith.  This conviction of righteous certainty continues to plague mankind in the form of religious prejudice, intolerance, bigotry, hatred, and violence.  Religious pluralism and acceptance is necessary worldwide, in order to eliminate conflict between faiths.  Governments must be secular in order to avoid favoritism to any single faith.

Tribalism is the root of most human conflicts – the notion of “us” versus “them”, with thoughts and rhetoric which de-humanizes the enemy.  The bases for that tribalism are the familiar divides of race, religion, ethnic identity, national origin, wealth and political orientation.  Tribalism itself must be recognized as the enemy, and opposed wherever it occurs.

2)      Bring prosperity to all.

We cannot realize the full potential of mankind while a large portion of the world’ population lives in poverty.   Although great strides have been made in reducing extreme poverty, still, between one-third to one-half of the world’s population lives in poverty according to some measure – without access to adequate clean water, food, or sanitation. 

Health, nutrition, sanitation and education are the minimum requirements for full realization of a human life.  If not from the morality of fairness, then our own self-interest should motivate us to provide these things for all of humanity.  Because if we are to realize the potential of our species, we need the best performance from all of the workers, all of the scientists, and all of the geniuses on the planet.  If we do not provide these things to every young person, we are missing out on the possible contributions that we might receive. 

Although extreme poverty is diminishing, income inequality is increasing around the globe.  As economist Thomas Piketty pointed out, as long as the return on capital exceeds the rate of economic growth, the unequal distribution of wealth will increase.  Further, automation of labor through robotics and computerization is a threat to the global middle class, causing destruction of middle-income jobs.  The loss of honorable work is nothing new; it has been a theme of several dystopian novels, notably Kurt Vonnegut’s first novel, “Player Piano”, published in 1952.  Providing meaningful employment to workers will be a major economic challenge as labor is increasingly automated.  

Conflict is often rooted in inequity.   The final reason for bringing prosperity to everyone is to reduce conflict between people.  People naturally understand fairness.  People desire equality of opportunity, and a decent, honorable and respected quality of life.

The elimination of inequality includes the elimination of gender and racial discrimination.  Apart from the moral imperative of fairness, we must understand that we are unlikely to realize human potential if half of the human race is blocked from contributing to our success.   

Balancing the distribution of wealth is difficult.  It means providing equality of opportunity.  It means balancing the meritocracy of individual achievement with respect for all people.  It means providing meaningful and financially rewarding work to all laborers.  It means managing the disproportionate return on capital to the owners of capital with the need to distribute wealth throughout society.  By no means have we solved these problems, or have any solution in sight.  But providing honorable prosperity to everyone is something that we must do to achieve the potential of the human race. 

3)      Mitigate environmental damage.

Damage to our environment will shorten the lifespan of our technological civilization, reducing our chances of realizing our potential.  It should now be clear to everyone that human-induced climate change is real.  Our emissions of greenhouse gases are adding heat to the atmosphere and changing the climate in ways that may be very damaging to many people.  There is no quick fix, but we need to stabilize or reverse climate change by 2050.  Beyond climate change, we must remediate the damage to the ecosystems of the oceans due to overfishing and pollution.  We must also stop the absorption of CO2 from the atmosphere into the oceans, which is causing a significant change in ocean acidity.  We need to achieve clean air and water, particularly in newly industrialized developing countries which are rapidly causing damage to the environment.

We need to achieve our goals of environmental protection without compromising the standard of living and economic well-being of people.

4)      Continue scientific studies and space exploration.

Obviously, we will not explore and colonize space without further progress in science and technology.  We must continue to explore the planets, moons and asteroids of our solar system.  We need to continue to investigate the effects of the space environment on human physiology, so we can design spaceship environments capable of deep space flight.   We are making good progress in that direction, with concrete plans to send a manned mission to Mars.

I think an important stepping-stone will be to mine the asteroids, or bring asteroids into Earth orbit to provide construction materials for other ventures.  The technology required for these ventures will add to the general know-how of living and working in space.

Energy is a significant constraint in space exploration, as it is on Earth.  Small-scale nuclear fusion reactors seem feasible, and there are a number of research companies working on the idea.   When fusion energy is achieved, it will be a milestone for space exploration, as well as the key to ending our climate-change crisis on Earth.  For these reasons, continued funding and research into fusion power must be one of our special priorities. 

It is also not too early to think big – an independent, self-sustaining planetary colony may require a more accommodating environment than today’s environment on Mars or Venus.  Within this century, we could begin the first stages of terraforming Mars, Venus, or moons within our solar system.  The costs might be large, and it may require centuries, but the reward would be another home planet for mankind.

And private entrepreneurs are already working toward an interstellar exploration project.  The "Breakthrough Starshot" was initiated in 2016 by Russian entrepreneur Yuri Milner with a personal commitment of $100 million, and supported by Facebook founder Mark Zuckerberg.  The US agency DARPA has also given a grant called the 100 Year Starship, toward the development of the capability for interstellar travel within 100 years.

Conclusion

There is a lot to do.  But there are seven billion people capable of carrying the task forward.  We need to extend the lifetime of our technological civilization, we need to do more to ensure social equity and opportunity, and we need to work toward colonizing other planets.  The first thing is to recognize the goal and to gain alignment of many people toward that goal.

We should also acknowledge the progress that has been made over the past 300 years of the scientific enlightenment, and especially the incredible progress over the past 30 years in former "developing countries".  This progress is well documented in Hans Rosling's book Factfulness, and Steven Pinker's book Enlightenment Now.  Rosling's data visualization site Gapminder.org, is an excellent tool for seeing that progress, especially in the visualization "Health and Wealth of Nations".   https://www.gapminder.org/tools/#$chart-type=bubbles

We will not realize the potential of our species by focusing on self-interest or national interest.  We will not get there by fighting.  We will not get there by arguing about what is the correct religion and true form of God.

Although our entertainment about space provides inspiration, we will not achieve human opportunity by reading science fiction, or watching Star Wars, or playing space games.  It seems to me that people are satisfied with the dream, the fantasy that we are a space-faring people.  We will only achieve human opportunity by actually doing things that will bring us closer to space travel.

Entrepreneur Elon Musk recognizes the value and the fragility of human opportunity.  Musk made a fortune in Internet businesses with the purpose of acquiring enough capital to make a difference.  Musk started the automobile company Tesla, with the goal of reducing greenhouse gas emissions and mitigating environmental damage.  Musk founded the rocket company SpaceX, because Elon Musk sincerely wants to colonize Mars.   Few of us have the abilities or resources of Elon Musk, but everyone can do something. 

Against odds of a hundred billion to one, we stand today as perhaps the only technological civilization in the galaxy.  After three and a half billion years of evolution, we are alive at the very moment when we have the intellect and capability to do something remarkable – to remake the galaxy into a home for earthly life and mankind.  We stand on the brink of colonizing the stars.  Whether we succeed or fail depends on us.  

Let's do it.
-------------------------------------------
Original post: 7/13/2016.  
Edited 4/3/2020 to add references to Hans Rosling's Factfulness, and Steven Pinker's Enlightenment Now, and references to interstellar exploration initiatives, and additions about human potential.
---------------------------------------------

References:

Drake Equation

https://en.wikipedia.org/wiki/Drake_equation

N = R_* ^. f_p ^.n_e ^. f_l ^. f_i ^. f_c ^. L

where:

N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);

and

R_* = the average rate of star formation in our galaxy

f_p = the fraction of those stars that have planets

n_e = the average number of planets that can potentially support life per star that has planets

f_l = the fraction of planets that could support life that actually develop life at some point

f_i = the fraction of planets with life that actually go on to develop intelligent life (civilizations)

f_c = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L = the length of time for which such civilizations release detectable signals into space

Drake Equation Calculators

http://www.classbrain.com/artmovies/publish/article_50.shtml

http://www.as.utexas.edu/cgi-bin/drake.pl

http://www.bbc.com/future/story/20120821-how-many-alien-worlds-exist

Planets Image

http://www.cosmosup.com/fascinating-planets-outside-the-solar-system/

Origin of Life on Earth

http://scitechdaily.com/new-evidence-on-the-origins-of-life-on-earth/

https://en.wikipedia.org/wiki/Abiogenesis

Origin of life at least 3.5 billion years ago, possibly as old as 4.1 billion years ago.  Probably originated as RNA-based life.  Gained complexity and diverse functions through time.

https://en.wikipedia.org/wiki/Eukaryote

https://en.wikipedia.org/wiki/Multicellular_organism

Multicellular life evolved independently at least 46 times.  Multicellular life arose about 3 to 3.5 billion years ago, and complex multicellular life arose about 1.5 billion years ago. 

https://en.wikipedia.org/wiki/Human_evolution

Homo habilis: 2.8 m.y. BP

Progress

Hans Rosling, 2018, Factfulness, 341p.
Hans Rosling, Ola Rosling, Anna Rosling Ronnlund; Gapminder.org.

Steven Pinker, 2018, Enlightenment Now, 576 p.

http://data.worldbank.org/indicator/MS.MIL.XPND.GD.ZS

World Bank statistics on military spending, as a percentage of GDP by country.  

Military spending is still increasing in real terms, due to the increase in global GDP.  Real military spending has increased by 2.5x since 1988.

World military spending declined from 3.4 percent of GDP in 1988 to 2.3 percent in 2015.

United States military spending has declined from 5.6 percent of GDP in 1988 to 3.3 percent in 2015.

http://www.worldbank.org/en/topic/poverty/overview

The number of people in extreme poverty has been falling rapidly.   In 1981, 44% of the world’s population lived on less than $1.90 per day.  By 1990, that number was reduced to 37% of the world’s population, and by 2012, only 12.5% of the world’s population lived on $1.90 per day. 

http://www.globalissues.org/article/26/poverty-facts-and-stats

In 1998, over 80% of the world’s population lived on less than $10 per day. 

Space Exploration

http://waitbutwhy.com/2015/05/elon-musk-the-worlds-raddest-man.html

http://waitbutwhy.com/2015/08/how-and-why-spacex-will-colonize-mars.html

https://www.tesla.com/blog/master-plan-part-deux

https://www.tesla.com/blog/secret-tesla-motors-master-plan-just-between-you-and-me

Several articles from a series about entrepreneur Elon Musk.

http://curious.astro.cornell.edu/about-us/150-people-in-astronomy/space-exploration-and-astronauts/general-questions/921-how-much-money-is-spent-on-space-exploration-intermediate

Most information seriously dated – 2005 vintage.

https://en.wikipedia.org/wiki/Budget_of_NASA

NASA 2016 budget:  19 billion dollars.

https://www.spacefoundation.org/sites/default/files/downloads/The_Space_Report_2015_Overview_TOC_Exhibits.pdf

Total global spending for space products and services was $330 billion in 2014, including commercial, military, and government scientific spending.

Given global GDP of 74.150 billion in 2015, spending on space is about 0.4 percent of global GDP.

Interstellar probes
- http://www.scientificamerican.com/article/100-million-plan-will-send-probes-to-the-nearest-star1/

- https://breakthroughinitiatives.org/Initiative/3

https://singularityhub.com/2017/06/18/why-interstellar-travel-will-be-possible-sooner-than-you-think/

https://en.wikipedia.org/wiki/Breakthrough_Starshot

https://en.wikipedia.org/wiki/100_Year_Starship