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Tuesday, March 21, 2017

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. 
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


Launch Costs



Image credit

NASA Psyche Mission
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)




Asteroid Mining
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. 

Kepler Energy and Space Engineering

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.



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