August 28, 2015

How We Choose our Near-Earth Asteroid Targets

When traditional mining companies evaluate a potential mining target, they have a couple thoughts in mind:

(1) Is it technically feasible? (2) How much will it cost? (3) How much risk is involved, and (4) Will it yield a profitable return?

In choosing an asteroid target for mining in space, the goals are the same, but the variables can be much different.

In both traditional mining and asteroid mining, we are all after the same thing: ore.


One of the 13,000+ physical samples housed in the Lamont Deep Sea Sample Repository at the Lamont–Doherty Earth Observatory. Image Credit: Kkostel


Geologists analyze core samples from their project site. Image Credit: Oregon Department of Transportation

An ore is any material that can be recovered from a mining or drilling site and sold for a profit. On Earth, most ores tend to be a metal such as gold, platinum, copper or uranium, but in space, water can also be considered an ore because it can be recovered from an asteroid and sold for a profit.

In space, water is one of the most precious resources as it is essential for human survival and provides a method of efficient transportation. Water can be used to grow food, shield astronauts from radiation, and even as a source of fuel for rockets, satellites, and deep space probes.

When prospecting for energy or minerals on Earth, you have a huge array of sophisticated tools at your disposal: soil samples, seismic surveys, electromagnetic and gravity surveys, as well as aerial and satellite imagery. You can also send out a ground crew to actually walk the area you are prospecting, and drill core samples.  The result is a set of data that allows the mining company and potential investors to make an informed decision on moving forward with the project, or moving on to another prospect.

Mining requires prospecting, on Earth or in space, and it works a bit differently in space.

We begin just as any mining exploration activity does – by finding all the available data we have today. Over the past 20 years, scientists have identified over 11,000 near-Earth asteroids (in addition to the near million we know of in the Main Belt). Planetary Resources is targeting near-Earth asteroids for our prospecting and mining missions because they are energetically closer to Earth than Main Belt asteroids, therefore making the trip to rendezvous with them much easier.


Near-Earth Asteroid Orbits_Planetary Resources

Here is an illustration that shows the three typical orbit patterns of near-Earth asteroids. You can see that the Aten, Amor and Apollo orbits come very close to, and sometimes intersect, with the Earth’s orbit. When this occurs we observe them and can even rendezvous with them with our Arkyd spacecraft. Credit: Planetary Resources, Inc. 

When they pass by Earth, scientists have also discovered what near-Earth asteroids are made of through the use of remote sensing technology which can produce images like this:

Scientists also can analyze asteroids using Radar, which produces an image like this from a recent close fly-by of asteroid 1999 JD6 obtained on July 25, 2015. The asteroid is between 660 – 980 feet (200 – 300 meters) in diameter. Image credit: NASA/JPL-Caltech/GSSR


Using this pre-existing data, we have been able to create a target list of the top asteroids that we now are tracking and evaluating for further prospecting.

Factors that Makeup a Good Asteroid Target

1999 JU3 is on Planetary Resources Target list. It is a known carbonaceous asteroid that is predicted to be worth trillions. Image Credit: Planetary Resources, Inc.

Once an asteroid has either been prospected from Earth, or one day soon by our Arkyd prospecting spacecraft, there are a few main variables that we evaluate to determine if an asteroid is a viable target or not.

Delta-V: low change in energy means we can pack more tools, and less fuel.

Delta V, also known as the “speed limit of space” is an important factor to consider.

For our Arkyd spacecraft capabilities, we look for asteroids with low Delta-V, less than about 5 km/s. This allows us to use more of the mass on Arkyd on the important tools needed for the mission, and less on fuel needed to rendezvous with the asteroid.

Spin rate: if it spins like a top, it is not a good target.

Asteroids with a slower rotation are vastly preferred. Although there are not many that are considered large enough for our target list that also spin quickly. If they are spinning “like a top” typically this means the asteroid experienced some sort of collision. You may remember this story from earlier in the year of asteroid P/2012 F5 that was spinning so much, it disintegrated.

Size: bigger is better…to a certain degree.

Our targets are typically about 300 meters across to ensure that the missions produce enough ore or H2O to be worth the cost and effort.

Most near-Earth asteroids are much smaller, making the ones large enough a bit harder to come by.

Orbit: the asteroid must stop by Earth often.

A good asteroid target will have an orbit that revisits Earth often, and is typically not inclined.  Even if it has an Earth like orbit, but it is inclined (tipped relative to the Earth’s orbit around the Sun) it makes it a much harder to rendezvous with it for prospecting operations.

2008 EV5 could be a spectacular asteroid when considering almost every other variable (good type, good delta-v, etc.), but it’s inclined, so you can only get to it for a few years every decade which is much longer than our preferred mission timelines.

Type: the asteroid’s composition.

The type of asteroid we are targeting today in our prospecting missions is a C-type. This type is potentially up to 20% water by mass, and is the perfect source for rocket fuel.

The other two types of asteroids out there are S-Type (Stony) and M-Type (Metallic). In future missions, we will also be targeting M-Type asteroids for their structural metals like Iron, Nickel and Cobalt which can be used to build structures in space with 3D printing.

Good Targets VS Non-Ideal Targets

This table explains the specific differences for each variable we use to analyze our targets of interest, when considering a “good” target and a “non-ideal” target near-Earth asteroid:


Here are some examples of asteroids we know quite a bit about today, one of which is a “good” target on our target list, and one that is a “non-ideal” target:

Asteroid that makes a “good” target: 1999 JU3

1999 JU3 has made the news recently, as the Japanese Space Agency, JAXA, has launched the Hayabusa 2 mission with plans to return samples of the C-type asteroid to Earth in 2020.

This asteroid is a target on our list because of its low Delta-V, large size, modest rotation rate, and it is a known C-type.

This video shows Earth’s orbit (in blue) relative to the asteroid’s orbit (in grey), as well as how a spacecraft would rendezvous with the asteroid (in green). Image Credit: NASA ARC 

Asteroid we will let pass us by: 2010 SO16

This asteroid is not on our target list because of its high inclination to Earth’s orbit, and infrequent revisit rate, even though as an Earth co-orbital body it remains an interesting asteroid to study.

This video shows Earth’s orbit (in blue) relative to the asteroid’s orbit (in grey), as well as how a spacecraft would rendezvous with the asteroid (in green). Image Credit: NASA ARC 

We need to learn more about the near-Earth asteroids on our target list.

In order to grow our target list with more certainty, we are developing advanced asteroid prospecting technology at our spacecraft factory in Redmond, WA. Right now, we are building the Arkyd rendezvous prospectors – highly capable, low cost spacecraft that will be equipped with hyperspectral and infrared sensors. These “space drones” will swarm prospective targets and collect information on the composition of the asteroid, analyze that information on the spot, and send back the answers to our team here on Earth.

The first step in the development of this technology is being tested today in low-Earth orbit. The Arkyd 3R was deployed from the ISS in July, and is now fulfilling its mission to test several of the underlying technologies we will use for the the Arkyd spacecraft.

Scheduled for launch later this year, the Arkyd 6 (A6) is a slightly larger spacecraft that will carry our first infrared imaging sensor which can be used to identify water resources on asteroids. This sensor has the ability to precisely measure temperature differences of objects. We will use it to acquire key data related to the presence of water, ice and water-bearing minerals.

Arkyd 6, launching later this year.

Arkyd 6, launching later this year.

In the process of gathering additional data through our prospecting mission, we can begin to define the mission profile for extraction, and determine the final scope, cost, difficulty, and feasibility of the mission.

As we continue to gain more intelligence on the near-Earth asteroids and develop our prospecting technologies, we will undoubtedly add even more exciting targets to our already growing list.

-Caitlin O’Keefe

Director of Marketing

Planetary Resources, Inc.