Why Asteroids are the “Low Hanging Fruit of the Solar System”

Earth is finite, but our economic growth need not be.

Asteroids will fuel a mass-constrained economy in orbit and back on Earth. In orbit, spacecraft propellant is a multi-billion dollar industry with each pound of fuel worth more than an equivalent pound of gold on Earth. Certain asteroids are loaded with hydrogen and oxygen, the components of rocket fuel. These asteroids can provide a fuel source that is 100 times closer energetically to Earth orbit, and thus far less expensive, than the Apollo-Era “bring-everything-with-you” propellant used today.

Back on Earth, platinum group metals are necessary for everything from catalytic converters to jewelry to the construction of electronics, medical devices, glass, and turbine blades. Despite their high price tags, these metals are used to manufacture one in four goods that we use everyday.

Today, the major sources of platinum group metals are concentrated in South Africa and Russia, and becoming increasingly hard to access over time. But in space, a single 500-meter platinum-rich asteroid contains more platinum than has been mined in the history of humanity. Planetary Resources is building the technology to access these resources today. Learn more about how Asteroid Mining will fuel human expansion into the Cosmos. 



Discovery & Quantity

Millions of asteroids silently glide near Mars and Jupiter’s orbital slots and, over time, gravitational perturbations kick some of these asteroids closer to the Sun, creating the class of objects known as near-Earth asteroids.

Near-Earth Asteroids

Near-Earth asteroids (NEAs) are generally defined as that population of asteroids which spends at least part of each orbit between 0.983 and 1.3 Astronomical Units from the Sun (1 Astronomical Unit is the Earth’s distance from the Sun). These asteroids were previously part of the Main Belt population or were once active comets.

In 1960, only 20 near-Earth asteroids were known, growing to 134 by the year 1990. Today, nearly 13,000 near-Earth asteroids are known to exist, and the number increases daily. Scientists believe the number may actually exceed one million. Of the asteroids currently observed, 981 of these objects are larger than one kilometer in diameter. The majority of the remaining known near-Earth asteroids are believed to be between 100 m and 1 km in diameter, with those smaller than 100 meters wide numbering slightly more than 2,800.

Near-Earth asteroids are categorized into three groups based on their distances from the Sun: the Atens, Apollos, and Amors. Some near-Earth asteroids spend nearly all of their time outside Earth’s orbit, while other objects, known as earth-crossers, have orbits that intersect Earth’s orbit.

This diagram shows three common orbit types for near-Earth asteroids: Apollo, Amor and Aten.

This diagram shows three common orbit types for near-Earth asteroids: Apollo, Amor and Aten.

Two near-Earth asteroids have been visited by robotic spacecraft: 433 Eros by NASA’s NEAR mission, and 25143 Itokawa by Japan’s Hayabusa mission. NASA is currently working on the OSIRIS-REx mission to visit the carbonaceous asteroid 1999 RQ36 in 2019. Our telescopic capabilities for asteroid observation are also improving. One example is the Large Scale Synoptic Telescope (LSST) that recently received a $20 million gift from Planetary Resources investor Charles Simonyi.

Near Earth Asteroids (NEAs) are the low-hanging fruit of the solar system, the easiest of all space resources to both access and return from.  There are over 42 trillion tons of resource that approach within 45 million km of Earth’s orbit. More than 13,000 NEAs have been identified and studied in some detail, and it is from this group that our first wave of exploration targets will be found.

To put 42 trillion tons of resource into perspective, let’s take, for example, iron ore. It is one of the most abundant minerals on earth, comprising over 5% of the Earth’s crust. The United States Geological Survey (USGS) estimates that there are 800 billion tonnes of iron ore worldwide. NEAs therefore represent a potential mineral resource at least fifty times larger than the Earth’s entire iron ore reserve.

And what does 45 million km from Earth really mean? The moon is approximately 384,000 km away from Earth, so these resources are within approximately 110 lunar distances of earth.

While 110 lunar distances may sound like a long way, it is important to think in terms of energy, not just distance. The majority of energy expended in space travel, over 60%, is utilized in just getting off planet Earth and orbiting at those first 200 km of altitude. Another 30% is needed to escape from Earth’s gravitational influence, leaving less than 10% of total required energy to navigate interplanetary space and rendezvous with the closest NEAs.

Or to put it another way – over half of the 13,000 known NEAs are energetically closer than the surface of the Moon. Our celestial neighborhood is more crowded – and closer – than you think!

Main Belt Asteroids

Main Belt asteroids are what most people envision when they hear the word “asteroids.”  Millions of Main Belt asteroids reside in a ring-like region between the orbits of Mars and Jupiter.  While these asteroids are important for understanding the early history of the Solar System,  they are not as easy to reach as the near-Earth asteroids.