Quark Matter in the Solar System

Quark Matter in the Solar System : Evidence for a Game-Changing Space Resource

T. Marshall Eubanks Asteroid Initiatives LLC, Clifton, Virginia ([email protected])

January 9, 2014 IAA Space Exploration Conference Washington, D.C.

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Outline of Talk • Introduction • Quark Matter Nuggets ◦ Basics of Quark Nugget theory ◦ Current Limits on Quark Nuggets • Quark Matter and the Solar System ◦ Capture of Dark Matter in the Proto-Solar Nebula ◦ How to find Quark Nuggets in the Solar System • Evidence for “Strange Asteroids” ◦ The Anomalous Rotation of Small Asteroids • “Solar Prospectors” - Finding Ultra-Dense Asteroids by Spacecraft • Conclusions : A Game-Changing Possibility for Space Exploration.

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Introduction

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What is Dark Matter? • Observations reveal a serious failure of physics at large astronomical scales (galactic disks and halos, clusters of galaxies and larger). ◦ Apparent gravitational accelerations on these scales are consistently larger than can be explained by the matter we can see (stars, gas, etc.). − This appears to be totally separate from the “dark energy” required to explain a relatively recent acceleration in the expansion of the universe. • If these accelerations are attributed to some non-interacting (or “dark”) form of matter, then roughly 84.5 % of the matter in the universe is dark. ◦ There have been many proposals to explain these discrepancies in terms of new particles from new physics. − E.g., WIMPS (Weakly Interacting Massive Particles) ◦ After decades of searching, there is no conclusive evidence that any such particles exist. ◦ The field is wide open for alternative explanations.

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Quark Matter : A Game Changing Resource in Solar System? • Quark Nuggets are an alternative explanation for Dark Matter with profound implications for the exploration of the Solar System. ◦ There are numerous theories predicting that nuggets of condensed quark matter (“QBalls,” “nucleates”) would be left over from the early universe. ◦ The Quark Nugget theory used here is that of Zhitnitsky [2003a,b], which makes specific and testable predictions. • There is as yet no proof that Quark Nuggets exist, but there is some suggestive evidence from Solar System observations. • What is the relevance of this for Space Exploration? ◦ If there is a significant density of primordial condensed quark matter, there will be some in the solar system (including in asteroids). ◦ Asteroidal Nuggets could be found using existing space technology − Asteroid Initiatives intends to search for these in the near term by sending spacecraft to selected asteroids. • Searching for them is a huge bet on the future, as quark matter, if found, could be “mined” for antimatter (currently valued at $ 65 trillion USD / gram). 5

Quark Matter Nuggets

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The QCD Era in the Early Universe • Quark Nuggets are a new version of an old idea. ◦ The idea that condensed quark matter could form in the early universe and persist until the present has a considerable history, dating back to the “quark nugget” proposal of Witten [1984]. − Other names for similar proposals are stranglets, nuclearites, Q-Balls.. • Quark Nuggets would be relics of the “QCD epoch,” the period during the first 10 µseconds after the Big Bang when there were no baryons (protons, neutrons), but instead a quark-gluon plasma (QGP). ◦ At that time the Hubble distance, RH , was ∼ 10 km. ◦ The density was > 4 × 1017 kg m−3 (the nuclear density). ◦ The temperature was ∼ 160 MeV (1.9 × 1012 K). ◦ The redshift, z, was ∼ 1012 . • This represents the point, as the universe expanded and cooled, when quarks became confined and the QGP froze out into hadrons, forming protons and neutrons. • If quark matter is stable (or sufficiently metastable) material from that epoch could still exist today. 7

Basics of Zhitnitsky Quark Nugget theory • In the Zhitnitsky theory stable Quark Nuggets would be formed in a fairly narrow range of masses. ◦ The lower mass limit is set by the stability of the Quark Nugget against decay and the upper mass limit by the requirement that the quark matter be compressed to greater than nuclear density. ◦ The stable Quark Nugget mass range is determined by fa , the axion decay constant. The current uncertainty in fa [Laki´c et al., 2012] constrains the stable Quark Nugget mass, MQ , to 105 kg . MQ . 4 × 1010 kg. − I will show evidence that MQ is ∼ 1010 kg, implying a value for fa at the upper end of the allowed range. − Note that a 10 megaton Quark Nugget would have a radius of only 1 mm. • Zhitnitsky and his colleagues favor a small value for MQ , ∼ 1 gm, so that Quark Nuggets could explain various anomalous radiation features in in the Galaxy [Forbes and Zhitnitsky, 2008a,b, Lawson and Zhitnitsky, 2013]. ◦ Such small Quark Nuggets would be inherently metastable, but normal matter nuggets could merge, absorb ordinary matter, and grow to the maximum mass.

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Current Limits on Quark Nugget Dark Matter • There are a variety of prior limits on Quark Nuggets as dark matter, which can be divided into three mass ranges. • Low mass limits (MQ ¿ 1 gm) come from laboratory searches for dark matter. ◦ The current best such limits are from the MACRO Collaboration [2002], which disallow Quark Nuggets smaller than ∼ 10 milligrams. • Mid-range (kg to ton) limits come from seismology [Herrin et al., 2006]. • Finally, at the upper end of the mass range (planetary masses) there are limits from gravitational µlensing [Alcock et al., 1998], and (for primordial Quark Nuggets) from the requirement that Quark Nuggets could not be larger than the horizon at the QCD era [Madsen, 2006] • All of these constraints are consistent with the Quark Nugget mass range allowed by the Zhitnitsky axion domain wall theory.

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Limits on Quark Nugget Dark Matter 1e-05

1

Mass (kg) 100000 1e+10

1e+15

1e+20

1e-21

ρQ (kg m-3)

VFR Asteroids

MACRO

Kepler

Axion Domain

1e-22

µLensing

Wall Apollo ALSEP ρCDM (Halo) USGS µLensing 1e+20

1e+25

Femtolensing

Model Mass Range

1e+30

1e+35

1e+40

1e+45

1e+50

Baryon Number(B)

This figure assumes a monochromatic Quark Nugget mass spectrum. The Halo CDM Density is 10 from local stellar kinematics [Bovy and Tremaine, 2012]. Note that the experimental “asteroid constraints” and the theoretical “axion domain wall mass range” are consistent with each other and with all the other experimental constraints.

Quark Matter and the Solar System

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Why should there be Dark Matter in the Solar System? • Dark matter (whether microscopic or macroscopic) would be included in the Solar System primordially (from its formation). • Planetary systems such as the Solar System appear to form in the collapse of molecular clouds as they cool. • A small portion of the dark matter inside the collapsing cloud would have (by chance) relative velocities . 5 km sec−1 , and would be subject to capture. ◦ Primordial capture probabilities are ∼ 2 × 10−4 and 3 × 10−6 for dark disk and Halo dark matter, respectively. ◦ The total amount of primordially captured dark matter would be ∼ 10−6 M¯ or ∼ 3 × 1024 kg), with ∼ 98% of the captured material coming from the dark disk. ◦ That corresponds to ∼ 3 × 1014 (1010 kg/ MQ ) Quark Nuggets. • With their large superconducting gap energies, there is nothing to stop these Quark Nuggets from beginning to accrete normal matter mantles, forming “strange planetesimals.” ◦ Bodies with radii . 100 meters would have most of their mass coming from their strange matter cores and would be truly “strange asteroids.”

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How to find Quark Nuggets in the Solar System • Most Quark Nuggets in the Solar System should be currently located in the center of the Sun and planets, where they would be hard to detect, and even harder to reach. • Small (. 200 meter radius) strange asteroids, if they exist at all, are both more likely to both reveal their Quark Nugget cores and (if detected) could be suitable for direct exploration by spacecraft. • Asteroids can be strongly perturbed by radiation pressure, both the Yarkovsky effect [Vokrouhlick´y et al., 2000], thrusting which changes orbits, and the Yarkovsky-OKeefe-RadzievskiiPaddack (YORP) effect [Bottke et al., 2006], torquing of asteroidal rotation. • A small strange asteroid would respond very differently to Yarkovsky and YORP perturbations. ◦ The mass would be increased over an ordinary matter body of the same size, which would decrease Yarkovsky accelerations; such objects would have a longer residence time in NEO orbits. ◦ The moment of inertia change would be negligible, so there would be nothing to stop YORP spin-up of rotation period. ◦ AND, a small strange asteroid would have a higher than expected surface gravity, and thus would be more resistant to rotational disruption, and thus could be spun up very fast. 13

Asteroids and Quark Matter • I originally thought that asteroid observations would be a good way to disprove the massive Quark Nugget theory, and that this would make a nice, quick, paper. However ◦ Fast rotating small asteroids are very common, with the shortest known period being 25 seconds. ◦ It turns out that these asteroids could avoid disruption if they possessed Quark Nuggets with masses in / near the stable range predicted by the Zhitnitsky theory, which of course is completely independent of any asteroidal data. • It is fair to say that this surprised me.

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The asteroid rotation period-radius relation 0.01

Rotation Period (Hours)

0.1 1 10 100 1000 10000 0.001

NEO Main Belt Trans-Neptune Objects Comet-Like Orbits RPL (2.2 hr) Very Fast Rotator Limit (0.5 hr) 0.01

0.1

1

10

100

1000

Asteroid Radius (km)

The change in the character of asteroid rotation rates at R ∼ 200 m is obvious to the eye, with most asteroids with R < 200 m having rotation periods < 1 hour while almost all asteroids with R > 200 m have periods & 2 hours. The horizontal solid line is the Rubble Pile limit for a uniform density of 2300 kg m−3 , and the horizontal dashed line is the 0.6 hour VFR limit.

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Estimating Core Masses from Asteroid “Rubble Pile” rotation limits • Assuming a lack of internal cohesion it is straightforward to take the observed radius and rotation frequency and estimate the mass of the Quark Nugget core, MQ , (assuming a default density, ρO , for the ordinary matter mantle, and, e.g., a spherical body). • This indirect mass estimate is not as firm as a direct mass estimate (say, from an orbiting spacecraft), but it can be done for numerous bodies. • When this is done the centroid of the MQ distribution is ∼ 2 × 1010 kg within the range predicted by the Zhitnitsky theory for stable Quark Nuggets. • This agreement between theory and observation is not proof, but it is powerfully suggestive.

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Quark Nugget Core Mass Histograms from Asteroid Rotation 1e+06

Mass (kg) 1e+10

1e+08

1e+12

30

# Asteroids / Bin

R < 50 m R > 50 m

Axion Model

25

1e+14

Prediction

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15 Range for Maximum fa

10

5

0 32

34

36

38

40

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Log 10 Baryon Number

Histogram of the Quark Nugget core mass required to prevent rotational disruption assuming gravitational binding and no internal tensile strength, for two independent sets of asteroids. These core mass estimates are based on a rubble pile model with a default ρ = 2300 kg m−3 for all asteroid mantles. Also shown (as vertical lines) is the Quark Nugget mass range allowed by the axion domain wall theory given current experimental constraints on the axion delay constant fa and, as marked, the narrower range consistent with the maximum allowed value [Wantz and Shellard, 2010] for fa (2.8 × 1011 GeV). 17

“Solar Prospectors” Finding Ultra-Dense Asteroids by Spacecraft

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Strange Asteroid Prospectors • What is the best way to confirm (or refute) the existence of Quark Nuggets in the NEO? ◦ The best way to confirm the existence of strange asteroids would be simply to visit them. ◦ With a low speed rendezvous, or after going into orbit, it would be straightforward to determine the mass and density of a strange asteroid candidate. • From the current set of asteroids in the Light Curve Database, we have identified 12 strange asteroid candidates with ∆ V . 6 km / sec relative to the Earth. • Preliminary design work indicates an adequate prospector spacecraft could have ◦ Mass < 50 kg, with a payload mass < 3 kg ◦ Payload would be cameras. 1 kg would be potentially available to partners • Such small prospectors would be similar to the proposed BEE / APIES spacecraft swarm of D’Arrigo and Santandrea [2004] ◦ ESA considered solar sails, but went with more proven technology. • With the upcoming flight of the Sunjammer, solar sail propulsion seems very competitive for a swarm of prospectors. 19

Conclusions • There are both theoretical and observational reasons to believe that there is condensed quark matter in the Solar System. • If such matter is locally available, it can be found and used for scientific research and resource (energy) extraction. • Phenomenal amounts of energy are potentially available. A 1010 kg Quark Nugget could potentially yield megatons of antimatter. • Although the proposition is risky, the potential payoff would be immense. This is truly a game-changing possibility for space exploration. • Asteroid Initiatives is seeking partners and funding to prospect the Near Earth Objects for ultra-dense strange asteroids. ◦ The information gained from these prospectors would also be valuable for more conventional mining.

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