NASA Selects Two Asteroid Missions

by Paul Gilster on January 6, 2017

Among the five finalists for NASA’s Discovery program, I had become attached to the Near Earth Object Camera (NEOCam), whose purpose was to expand our catalog greatly, with the potential, according to mission backers, of finding ten times more NEOs than we’ve found to date. We’ll see if NEOCam has a future (I’ve just learned that it has been given extended funding for an additional year by NASA), but for now NASA has announced two other Discovery-class missions, both of which have objectives among the asteroids.

Lucy, scheduled for a launch in the fall of 2021, is to be a robotic mission with the goal of exploring six of the Jupiter Trojan asteroids. The Trojans share Jupiter’s orbit while moving swarm-like around the planet’s L4 and L5 Lagrangian points. Over 6000 Jupiter Trojans are now known, but the population is thought to be vast, with as many as 1 million Trojans larger than 1 kilometer in diameter. As to their origin, there is much to learn. They may be captured asteroids or comets, or as this short NASA video explains, even Kuiper Belt Objects.

From the standpoint of Solar System evolution, the Trojans make for interesting science. They’re relics of the primordial material of the outer system, and I see that principal investigator Harold F. Levison cites the mission’s name in connection with another Lucy, the fossil fragments that have been so significant in our understanding of human development. We’ll see if this Lucy gets as much public attention as its namesake, which acquired its name from the Beatles song ‘Lucy in the Sky with Diamonds,’ played at the recovery site in Ethiopia. Breaking out the Sgt. Pepper album on this Lucy’s arrival at its first target seems a natural.

There are connections between the Lucy effort and the highly successful New Horizons mission, in the form of later versions of the familiar RALPH and LORRI science instruments, and evidently several members of the Lucy mission team are connected with New Horizons as well. Lucy also benefits from the contributions of several members of the OSIRIS-REx team, the latter a robotic spacecraft now on its way to rendezvous with asteroid Bennu.


Image: (Left) An artist’s conception of the Lucy spacecraft flying by the Trojan Eurybates – one of the six diverse and scientifically important Trojans to be studied. Trojans are fossils of planet formation and so will supply important clues to the earliest history of the solar system. (Right) Psyche, the first mission to the metal world 16 Psyche will map features, structure, composition, and magnetic field, and examine a landscape unlike anything explored before. Psyche will teach us about the hidden cores of the Earth, Mars, Mercury and Venus.
Credit: SwRI and SSL/Peter Rubin.

The other mission is Psyche, dedicated to a single asteroid of that name that appears to be the survivor of an early collision with another object that violently disrupted a protoplanet. About 210 kilometers in diameter, 16 Psyche is thought to be composed mostly of metallic iron and nickel, a composition similar to the Earth’s core. We seem to be looking at what would have become the core of a Mars-sized planet, now without its outer rocky layers. Thomas H. Prettyman, a co-investigator on the Psyche mission, explains:

“Psyche is thought to be the exposed core of a planetary embryo – perhaps like Vesta – that initially melted and later cooled to form a central metallic core, silicate mantle, and basaltic crust. The outer layers may have been removed in a violent collision, leaving the core exposed. Psyche will provide a close-up look at a planetary core, providing new insights into the evolution and inner workings of terrestrial planets.”

The robotic Psyche mission will launch in the fall of 2023, with arrival at 16 Psyche in 2030 after two gravity assists, one from an Earth flyby, the second from a flyby of Mars. Both missions have this is common: They target the development of the early Solar System, one by observing the remnants of formation among the Jupiter Trojans, the other by seeing the interior of what might have become a planet. Let’s hope for the kind of success for both that we saw in earlier Discovery missions like MESSENGER and Dawn. OSIRIS-REx, meanwhile, is on course for a 2018 rendezvous with asteroid Bennu, with sample return to follow.


{ 44 comments… read them below or add one }

Larry Kennedy January 6, 2017 at 14:55

Very happy to see continued NASA interest in minor planets.


andy January 6, 2017 at 16:24

I’m glad the Psyche mission got selected, it will be interesting to see what a metallic world looks like up close.


Joy January 6, 2017 at 20:31

Certainly if there is ever a space power technology with the EROEI to support a technological civilization in space, there won’t be any shortage of already reduced nickle iron for megastructure construction.


LocalFluff January 11, 2017 at 11:52

Unfortunately it might be covered with regolith from other asteroids and look like any other asteroid. A lander would be nice, like DLR lander that Hayabusa-2 carries. But an orbiter to this odd ball is super great. It just cannot lead to no surprise.


James Benford January 6, 2017 at 16:46

The Trojans are a great place for ET to place a probe; hiding out among many rocks in a gravitationally stable place.


Michael January 6, 2017 at 17:40

yip, there could be a probe out there and we would not know it was there…mmmmm


Robert G January 6, 2017 at 21:30

But there are a lot of them there though.

Perhaps the trick to finding self replicating robot probes is to build one oneself, let it copy itself a bazillion times and then direct the resulting swarm to do an exhaustive search of a plausible location.

Sort of a self-qualifying e.t. search task.


andy January 9, 2017 at 13:01

I’ve seen assertions like this several times, but why are the Jupiter Trojans any better for hypothetical ET probes than, say, the main asteroid belt? Or the Hildas? Or the Neptune Trojans? Or wherever?


Alex Tolley January 9, 2017 at 14:33

Andy, I agree. Arguably a better place for a probe is one hidden in plain sight on the Moon’s nearside. In the last billion years or so, it would be pretty clear to a smart probe that Earth is going to be the planet of interest.

A replicator in the asteroid belt or even the Jupiter trojans will be fairly quickly discovered by a space faring race in the solar system. Therefore to stay hidden it must not replicate or obviously modify the resources. There is no obvious benefit pretending to be a rock out there compared to pretending to be a rock on the Moon.


ljk January 16, 2017 at 13:19

What if Earth’s Moon IS the smart alien space probe?

Cue The Twilight Zone theme music. Or The X-Files one.


Christopher L. Bennett January 6, 2017 at 16:48

It’s going to be very confusing to read about a mission where the probe and the asteroid it’s probing both have the same name (unless everyone commits to saying “16 Psyche” for the asteroid in every case).


Bruce Mayfield January 6, 2017 at 18:03

Good to see such missions moving foreward.

I have questions re trojan orbits about the L4 & L5 points: (1) How do objects move about these points? (2) How likely is it that earth massed exoplanets will be found in trojan orbits?


Neil Stahl January 7, 2017 at 11:47

As I understand it there are stable and unstable Lagrange points. Unpowered objects don’t stay around unstable LPs for long times but it doesn’t take much station keeping to hang around one. I understand objects orbit around stable LPs. I can imagine it’s kind of chaotic where this mission’s going.

Surely we’d have found any earth mass planets in LPs in our SS except maybe Planet 9’s.


Thomas Goodey January 7, 2017 at 12:50

(1) Jupiter’s L4 and L5 points, which is where this mission is going (I don’t know which) are stable.

(2) He said, EXO-planets.


Bruce Mayfield January 8, 2017 at 0:35

Yes. While these trojan ‘points’ are stable, they are not points of gravitational attraction, but just the center of regions of orbital stablity. I wonder therefore how hard or rare it may be for earth sized exo-planets to have accreted in the trojan regions of Super-Jupiters, BDs and Red dwarfs orbiting other stars.


Tom Pliska January 9, 2017 at 13:03

Crap! You just exploded my head when you suggested trojans for Planet 9. Vastness of space, and all. But has anyone done an analysis on how eccentricity of an orbit affects the likelihood a planet could have trojans?


andy January 10, 2017 at 15:38

As far as I’m aware, there are still exact Trojan configurations for eccentric orbits (basically so long as the three bodies remain in an equilateral triangle throughout their orbits, i.e. the periastron of the Trojan’s orbit is rotated by 60 degrees from that of the planet, with both planet and Trojan being at the same orbital phase), but I’m not sure how this affects stability. Plus the proposed processes for getting the planet into that kind of orbit (scattering or capture from another star) do not look promising for the survival of Trojans.

As for extrasolar systems, the most recent result I’m aware of is Hippke & Angerhausen (2015), where they claim there is tentative evidence that Trojans tend to be found around planets above ~60 days period, with an upper limit to the average transiting area of the Trojans corresponding to a body of radius ~460 km per planet (2σ confidence). Unfortunately the Kepler data is not sufficient to claim anything definitive about the occurrence of extrasolar Trojan planets.


Thomas Goodey January 6, 2017 at 19:30

“Psyche is thought to be composed mostly of metallic iron and nickel… We seem to be looking at what would have become the core of a Mars-sized planet, now without its outer rocky layers. Thomas H. Prettyman… explains “Psyche is thought to be the exposed core of a planetary embryo… The outer layers may have been removed in a violent collision, leaving the core exposed.”

How would such a collision strip away the outside but leave the metallic interior intact? That sounds a bit far-fetched to me.

An alternative, not palatable to current theorists, is that the planet(ary embryo), of which Psyche is the remnant core, exploded in some unknown way due to some unknown physics, blowing away all the overburden of silicates and ice and leaving only the metallic core. This was the contention of Thomas van Flandern, a dissident now dead.

One thing is for sure: Psyche must be the inner core of a much larger body, large enough to have had all that iron and nickel in it, which got hot enough (presumably because of aluminum-26) to melt and differentiate.


Bruce Mayfield January 9, 2017 at 20:53

“How would such a collision strip away the outside but leave the metallic interior intact?”

Yes, for ONE collision to have done that would have been hard, therefore it likely took steveral big hits to chip away at this old block. Some of the metallic meteorites found here likely came from Psyche.


ljk January 16, 2017 at 13:23

How does an explosion of a celestial object “in some unknown way due to some unknown physics” help in our understanding of how Psyche came to be exactly? Or lend any sort of scientific credibility in any way?

Is there any plausible way that a cosmic body like a planetoid could explode outside of a major collision? That is what needs to be investigated first. Saying it is unknown to current science is hardly enough.

And why does everything have to happen via explosion/collision? Clearly the Mythbusters program has saturated too much of our cultural thinking.


Thomas Goodey January 16, 2017 at 15:09

I didn’t say that my speculation was a full explanation. Nobody at the moment has any idea how such an explosion (not by collision) could occur. That doesn’t mean it should be completely ruled out.

A parallel to the thrust of my idea might be found in a classical book by Sir Arthur Eddington: ‘The Internal Constitution of the Stars’. This book made immense contributions to astrophysics, despite the fact that, when Eddington wrote it, nobody knew how hydrogen could be converted into helium while releasing a great deal of energy. Eddington frankly said that the mechanism by which energy of fusion could be completely released was completely unknown, but he (correctly) said that there must be such an unknown mechanism, to account for the energy radiated by stars.

And how would you propose that the outer layers could be stripped away, leaving the metallic core that is Psyche, other than by explosion or collision?


ljk January 16, 2017 at 18:14

Oh I think a collision would be the best bet, because the Sol system did and does those all the time, especially in the really old days.

As for the explosion idea, from this Wikipedia entry:

And I quote:

“The astronomer and author Tom Van Flandern held that Phaeton exploded through some internal mechanism. In his “Exploded Planet Hypothesis 2000″, he lists possible reasons for its explosion: a runaway nuclear reaction in uranium in the core, a change of state as the planet cooled down creating a density phase change, or through continual absorption of heat in the core from gravitons.”

Then there is my alien mining theory, which stopped at Psyche due to budget cuts.


Thomas Goodey January 17, 2017 at 5:12

I do not give much credence to TvF’s suggested possible causes for an explosion. Of course uranium wouldn’t be concentrated enough, and wouldn’t explode like that anyway. A phase change wouldn’t yield enough energy, and is not predicted by materials science. And LeSage gravitons are purely speculative.

Still, I don’t see how the outside layers of a planetoid could be “blasted off” by a collision, leaving the core intact.

I still think the possibility of a planetary explosion should not be completely dismissed. It is not practical to cite a known physical mechanism at this stage; fairly clearly, there is no such known mechanism. The point is that we do not yet know everything.


Daniel Suggs January 6, 2017 at 21:17

A chunk of mostly nickel and iron, 210 kilometers in diameter, sounds perfect for future asteroid mining operation.


Michael January 7, 2017 at 3:14

You could have a time drilling through it!


Phil January 7, 2017 at 4:53

Both great missions, but jeez,what does it take for Venus to get some love again?

Any idea which Trojan ‘camp’ the mission will be visiting,and which asteroids? This will surely have to be an ion powered mission, with a very big set of solar sails?



Paul Gilster January 7, 2017 at 12:05

Psyche is using solar electric propulsion — I assume the same is true for Lucy, but haven’t confirmed it. No solar sails, but presumably large arrays for power generation.


Bruce Mayfield January 8, 2017 at 9:39

“… what does it take for Venus to get some love again?”

Nicely worded Phil. An extremophilic lander/rover would be nice, but what does a robot need to be built from to survive in hot acid!?


Michael January 8, 2017 at 13:45
ljk January 16, 2017 at 13:30

The surface heat and atmospheric pressure are far more immediately deadly to a Venus lander than the sulfuric acid, as any Soviet Venera probe can tell you. Oh wait, they can’t. :^)

Two immediate ideas come to mind: The 90 Earth atmospheres of air pressure weighing down all across the surface of our neighboring world is equivalent to being half a mile below the surface of any Earth ocean, so while that is a lot of pressure, it is survivable as any modern terrestrial submersible device will attest. As for the 900 degree Fahrenheit heat, also global, a nuclear-powered cooling system could help here.

As for the sulfuric acid issue, an outer coating of stainless steel might do the trick, if it can also be modified to handle the heat:


Jens Knudsen January 17, 2017 at 19:03

Here is another one: But my first reaction when looking at Venus is something like ‘why bother?’ Even if we, a thousand or more years from now manage to restore(?) the Venusian atmosphere, and the planet becomes inhabitable, how are we going to put a magnetic field around it, to prevent the water from disappearing?


Michael January 19, 2017 at 15:34

If we had floating cities we could have powerful magnetic fields emitted from them as they float around the poles.


Frank Smith January 7, 2017 at 9:18

According to a Google search, scrap iron was going for about $92/ton in 2014.

A sphere of 210 km contains about 1.235 X 10^16 cubic meters.

One cubic meter of iron is a little under 4 tons.

So in 2014 prices Psyche is worth approximately 454.62 X 10^16 dollars, give or take a couple hundred trillion.


Thomas Goodey January 7, 2017 at 13:14

This is all wrong, in many ways.

The current price of iron, as of 06-Jan-2017, is $75.7 per tonne. See

But the value really depends what the material of Psyche actually is. It’s not pure iron. For example, steel is $300 per tonne. A recent price for nickel (on LME) is around $10,000 per tonne.

Iron density is 7.874 g/cm^3, twice what you said.

The mass of Psyche has been measured (from gravitational perturbations) as 2.27×10^19 kg^2. See Wikipedia. The “value” of this much pure iron would be about $170 x 10^16. But the nickel would make it much, much more “valuable”. And it may contain other good stuff. Who knows, there might be a substantial admixture of gold! And uranium!

This calculation is meaningless, however. First, Psyche is there, not here, and that is a serious obstacle. Secondly, we have no conceivable use for ten quadrillion tonnes of iron and nickel. If a considerable lump of Psyche were available, the prices of its ingredients would drop precipitously.


Frank Smith January 8, 2017 at 12:17

I should have known when I wrote my post some literal-minded soul was going to jump on my figures. I write a football fan blog and I get e-mails when I describe a player as 6-1 215. I promptly get told he’s actually 6-2 218!

Obviously, with the various uncertainties of Psyche’s composition any actual figures are going to be off by a lot.

My point was, if we ever develop a solar system economy, Psyche is probably going to be a valuable asset.

Back a number of year ago, the state office of mining claims in some state out West (Oklahoma?) was taking claims on asteroids . Wish I had been astute enough to put one in on Psyche.

The Chinese State Construction Company would have had to throw my descendants a couple of hundred billion dollars to avoid an epic legal battle :)


Jens Knudsen January 10, 2017 at 17:13

Psyche certainly makes me think of ‘astronomical amounts’ of building materials. A space based community could use a resource like this. But that point is more than likely driven home when, hopefully, we get the story from Psyche orbit.


Michael January 7, 2017 at 14:51

Could put a massive magnetic field on this object to collect hydrogen from the Sun.


John C Mruzik January 7, 2017 at 20:44

Excuse me, I am not very knowledgeable about this subject, but is it possible that it is magnetized?


Michael January 8, 2017 at 13:51

A magnetic field may have been frozen in BUT it must have been liquid at some point and may have exceeded its curie point and may not be.


Jens Knudsen January 10, 2017 at 17:09

Like the core of Mars?


Infinite123Lifer January 8, 2017 at 1:36

I remember reading an article on CD about polishing asteroids into some sort of optics and it being quite dreamy, also if I understood it correctly a swarm of smaller telescopes are more effective than one giant one but would this object be advantageous in those regards as opposed to rocky bodies?


Paul Gilster January 8, 2017 at 12:25

The article in question is here:

I have no idea how Psyche might be adaptable to this kind of concept, which is in any case a far future notion.


Jacopo Agagliate January 9, 2017 at 7:50

I’m probably being ignorant here, but I wish they’d subsidize asteroid exploration and possibly development to private companies while keeping their own focus on minor and “proper” planets. The future history of humanity and asteroids will arguably be one of industry, and at least in western countries where collectivist practices are not prevalent private interest should be actively jump-started as soon as possible. All the while, prime exploration targets like Venus, Titan and Europa sit there quietly, unloved (and no, fly-bys and orbital remote sensing are not enough).


John C Mruzik January 10, 2017 at 22:59

Thanks I understand.


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