A NEW MODEL OF MARS AS A FORMER CAPTURED SATELLITE:
BI-MODAL DISTRIBUTION OF KEY FEATURES
DUE TO ANCIENT TIDAL STRESS?
Richard C. Hoagland
(Principal Investigator,
Enterprise Mission)
Michael Bara
(Executive Director, Formal
Action Committee on Extraterrestrial Studies).
ABSTRACT
Conventional models of Mars, based on measurements by initial Mariner unmanned spacecraft, found an arid, apparently ancient environment without current liquid water. This prompted subsequent, highly negative assessments regarding Mars’ history, and the difficulty for the origin and/or evolution of higher forms of life. Later, the unmanned Viking missions (as well as the 1997 Pathfinder Lander) seemed to confirm this barren model. Complex, sometimes contradictory geologic theories to explain this desolate Mars environment have been proposed, based on a wide variety of observed surface phenomena and features. A new model that reconciles major puzzling contradictions among past models is now put forth, using new observations from MGS high-resolution images of Mars and a reevaluation of certain Viking era experiments. Small-scale surface features are identified which, it is proposed, are the direct product of wide spread ancient and recent bursts of subsurface liquid water. These water “stains” are shown to cluster (beyond statistical chance) in an unmistakable tidally-determined, bi-modal distribution on the planet: centered near the Tharsis and antipodal Arabia “bulges.” A revaluation of Mars ancient history is therefore proposed, suggesting that Mars (well after solar system formation) was captured into synchronous orbital lock with a larger planetary companion (“Planet V”), accounting for the clustering of present day water bursts around the former beds of two bi-modally distributed “Mars ancient oceans” as a direct result. The current Tharsis and Arabia mantle uplifts are shown to be an inevitable additional fossil signature of such former tidal stresses, induced by a close gravitational relationship with Planet V. Other heretofore inexplicable Martian surface features are shown to be consistent with such a simple "tidal model": Valles Marineris (as an eroded ancient tidal bore, formed immediately post-capture); the presence of the extremely flat terrain covering the northern hemisphere (via deposited sediments from the once tidally supported oceans, when released); and the current trench or "moat" around the Tharsis bulge (from relaxation of Tharsis back into the mantle, after tidal lock was broken). The long-mysterious “Line of Dichotomy” is explained as a remnant of a “blast wave” of debris from this sudden severing of the former orbital lock relationship with Planet V, due to either a catastrophic collision or explosion. Chemical signatures of this extraordinary destruction event on Mars are shown to be consistent with the model; including the distribution of olivine preferentially below the line of dichotomy; the presence of primitive mantle and core materials such as iron and sulfur in unusual abundance on Mars surface; and the concentration of proposed “water stains” in areas bereft of olivine. Mars unusual magnetic field “striping” is now shown to be another unique southern hemisphere signature of this destruction event, caused by standing P and S waves reverberating through the planet’s crust as a result of the massive simultaneous impacts from Planet V debris. Recently published research showing unprecedented outflow channels from the Tharsis and Arabia bulges are shown to be consistent with the sudden relaxation of the two tidal oceans, as is the sculpting of huge amounts of material by fluvial processes north of the Arabia bulge. Two possible mechanisms for the destruction of Planet V and the breaking of this tidal lock are outlined. Finally, a new timeline for Mars geologic evolution is proposed that is consistent with these observations, placing these events between capture ~500 MYA and the destruction of Planet V at 65 MYA.
Introduction
Man’s fascination with Mars has led
to many fanciful and romantic notions about the planet’s genesis.
Early popular (and even some scientific) speculations focused
on a planet populated by exotic creatures if not warring advanced civilizations;
these were based in large part on Lowell’s turn-of-the-Century model
of a harsh and frigid Mars, one that was still habitable, though dying. It was not until the 1964 Mariner 4 mission
that the general public and the scientific community got their first
close-up view of the real Mars -- as Mariner 4 flew by at a distance
of 6,118 miles. The 21 images
telemetered back to JPL surprisingly revealed a cratered terrain more
akin to the lifeless lunar surface than anything on Earth.
With these first insitu spacecraft Mars data, hopes for finding
anything approaching another “Earth” elsewhere in this solar system
were permanently dashed. Subsequent missions confirmed that the Martian
atmosphere was much too thin and the temperatures too low to allow for
the presence of surface liquid water, eliminating almost any remaining
hope of finding current life.
Eleven
years later, biology experiments conducted in 1976 by the Viking Landers
(including one termed the Labeled Release Experiment, or LRE), produced
positive results for life bearing organisms in the samples.
[1]
However, these findings were directly contradicted
by other instruments’ results, which indicated that the biology data
were “false positives,” generated by a non-biological chemical reaction
with the Martian soil.
[2]
Among the principal reasons cited for consensus
against the LRE was the absence of available liquid water on the Martian
surface – a key prerequisite
for life. This general dismissal
of the LRE results was immediately challenged by the LRE’s Principal
Investigator, Gilbert Levin. Levin
[3]
showed that liquid water could flow on the present
day Martian surface, if the available water was restricted to the lower
1-3 km of atmosphere, rather than being evenly distributed throughout
its depth. Meteorological data
from Mars Pathfinder later confirmed the Levin model for atmospheric
water distribution.
[4]
One
remarkable development in this regard has been the rediscovery of 25-year-old
“lost” NASA data from Levin’s own experiment.
Joseph Miller, a neurobiologist at the University of Southern
California, recently presented evidence that the radioactive C02 release
that was the heart of Levin’s experiment exhibited a clear 24.66-hour
Martian diurnal cycle – precisely the circadian rhythm to be
expected of living Martian microbes in the soil.
[5]
If confirmed, this would strongly indicate
current microbial organisms on Mars – despite a quarter-century of disclaimers
and the apparent dearth of liquid water.
In
striking contrast to the current apparent aridity of Mars, analysis
of images from Mariner 9 and Viking’s later Orbiters did reveal evidence
of large and catastrophic ancient water flows on Mars.
They also revealed evidence of a violent geological past -- with
huge volcanoes, extensive cratering in the southern hemisphere, and
a massive canyon system (Valles Marineris) stretching almost one-quarter
of the way around the planet.
Despite
evidence of wide-spread water flows on Mars, the general scientific
consensus now is that any liquid water on the planet has been confined
to the very distant past (circa 3 plus billion years -- GYA), when a
much denser atmosphere allowed it to flow freely across the surface.
The presence of large numbers of eroded craters in the south
is cited as proof that the planet has been geologically dead for at
least 3 billion years -- the time since the last “heavy bombardment”
of the inner solar system.
[6]
Figure 1 - MOLA colorized image of Mars showing the heavily cratered southern highlands (yellow and orange) and the smooth, sparsely cratered northern lowlands (blue and green).
Other
surface features present more difficult problems for geologists. There
are vast differences in crater densities between the northern and southern
planetary hemispheres. In the North, medium-sized craters are rarely
seen, with significant distances between them. This is in distinct contrast with the South, where craters are so
numerous that they overlap each other, making it difficult to distinguish
between individual impacts. This
stark difference is mysteriously emphasized by a “Line of Dichotomy”:
a separation line running around the circumference of the planet at
about a 35-degree angle to the Equator.
The southern, heavily cratered side of the line, is also (mysteriously)
nearly 30 kilometers (on average) higher than the northern sparsely
cratered lowlands.
Somewhat
limited by existing theories of solar system formation, planetary geologists
have tried to explain these major discrepancies on Mars in terms of
familiar models. Since the northern hemisphere accounts for
50% of the land mass but only 7% of the craters, the latest idea is
that Mars must have lost its “primordial crust” in the northern hemisphere
to an ancient
period of “vigorous convection and high heat flow”
[7]
early
in Martian history, at a time
well after the last heavy bombardment period.
However, the lack of smaller craters on the northern plains (based
on relative dating of similar cratering statistics from the Moon) paradoxically
implies a relatively recent date for this proposed “event.”
An Alternative Model of Solar System Evolution
In
1978, Naval Observatory astronomer and celestial mechanics expert, Thomas
Van Flandern, put forth the idea (based on an original model by
Olbers) that a relatively recent “exploded planet” in the asteroid belt
between Mars and Jupiter was responsible for the origins of most comets
and asteroids in the solar system.
[8]
This notion, called the Exploded Planet Hypothesis
(EPH)
[9]
, has found little support in the planetary science
community, but its lines of evidence since its initial publication over
twenty years ago have become increasingly compelling.
Part and parcel to this hypothesis is the idea that half Mars
visible surface was devastated by this proposed explosion event, neatly
accounting for the cratering dichotomy between the northern and southern
hemispheres, and the loss of a once dense and possibly life sustaining
atmosphere.
More
recently, writer Graham Hancock has popularized an alternative catastrophic
theory, which supports the conventional view that the north was stripped
of several layers of primordial crust.
[10]
Hancock argues that a large comet or planetoid
somehow wandered into the Roche limit zone of Mars and was drawn into
the planet in the Hellas basin, effectively tearing away the older surface
of the northern hemisphere via secondary bombardment, and depositing
the remnants of its shattered bulk into the southern highlands. Hancock’s idea is based on Donald W. Patten and Samuel L. Windsor’s
research,
[11]
who surmise that this object was in fact a “rogue
planet” they call “Astra,” described in their book “The Scars of Mars.”
There are however numerous problems with the “Astra” concept
– for instance, it cannot account for the presence of the asteroid belt,
while the EPH does so intrinsically.
The authors of this paper believe that the EPH is the much stronger
hypothesis (if appropriately modified), and that it has already demonstrated
a capacity to survive serious falsification efforts, qualities not shared
by “Astra.”
Extension of the EPH
Recently, Van Flandern has extended the EPH to include
the notion that several “planets” (Pluto, Mercury, and Mars) are actually
former moons of current or destroyed planets. Evidence to support this hypothesis is extensive,
but for our purposes we will focus exclusively on the evidence for Mars. Of these lines of evidence, we will address
here only a few as relevant to our proposal.
A more complete analysis will be left to a follow–on paper. Some of the evidence, as compiled by Van Flandern:
Dorman
& Woolfson (1977), writing in the Philosophical Transactions of
the Royal Society of London, resented a model called “the Capture Theory
of Planetary Formation.” They proposed that Mars was once an original
(not captured) moon of one of two colliding “protoplanets” in the early
accretion solar system phase.
[12]
They even provided one specific piece of evidence
to support their idea that Mars began as such a satellite: Mars density
is much closer to that of some of the Galilean satellites than it is
to Venus, the least dense inner planet.
This implies a genesis more in common with Io, Europa and Earth’s
Moon than with the terrestrial planets.
To quote Woolfson (1984):
“As part of the [Capture Theory] scenario, it has been suggested that Mars was originally a satellite of one of the colliding planets. The densities of the terrestrial bodies and some larger satellites are shown in support of this suggestion (Figure 2). Connell & Woolfson (1983) have ascribed the hemispherical asymmetry of Mars, like that of the Moon, to abrasion by high-speed ejecta from the planetary collision of that face of the satellite turned toward its primary. This will give rise to a thinning of the crust and for Mars such features as the centre-of-mass centre of figure offset are well explained by this. If Mars as a satellite was in synchronous rotation about its primary then this mechanism would suggest that its spin axis should be contained in the plane of asymmetry, but it is actually 55 degrees [the 35 degree line of dichotomy, minus 90 degrees] to that plane [emphasis added].”
Figure 2 - Terrestrial planets and larger satellites listed according to density. Mars is much closer to Earth’s Moon, Io, and Europa in density than it is to Venus, the first major terrestrial planet listed.
Van
Flandern’s EPH Model proposes that there were formerly two massive planetary
bodies in the current orbits of Mars and the Asteroid Belt, respectively. Both exploded. The first (Planet K) detonated in the orbit of the current Belt
“several hundred million years ago.”
The second (Planet V) exploded near the present day orbit of
Mars, some 65 million years ago (MYA).
In Van Flandern’s theory, additional impact damage was done to
Mars when a much smaller second former moon of Planet V exploded
in Mars vicinity 3.2 MYA. In
our modification of the EPH, we will show that it is not necessary to
invoke a literal planetary “explosion” to produce all the subsequent
effects Van Flandern has proposed, including the formation of asteroids
and comets, and the escape of most of the remaining mass from solar
influence. In doing so, we will
draw upon new data not available when Van Flandern originally formulated
his EPH ideas, specifically, observations of certain Extra Solar planets
that follow orbits similar to what we are proposing led to Mars initial
capture as a satellite, and then the destruction of its “foster parent,”
Planet V.
The relevance of water
If Mars, prior to its capture (in our
model) formerly had a denser atmosphere that provided for liquid water
on the surface, it is likely that this water – dependent on the amount
-- was distributed in lakes or oceans, much as it is here on Earth. If this was the case, there should still be pockets of this water
trapped beneath those former lake or ocean beds, relatively close to
the surface, dependent on how long ago the water actually flowed. If extensive “fields” of this frozen or (sometimes)
liquid water were discovered near the surface, this would strongly imply
such former “lakes” or “oceans” were the source.
Besides
Levin’s atmospheric model, the best evidence for current liquid water
near the surface of Mars (until recently) was provided by Dr. Leonard
Martin of the Lowell Observatory. Martin, in 1980, compared two images of Mars
taken from the Viking Orbiters that clearly showed an erupting water
spout.
[13]
This implied active geothermal heating of a
source of water not too far below the current Martian surface.
In June 2000, Michael Malin and Ken Edgett of MSSS published a paper in Science [14] , proposing that grooved features on cliffs and gullies on Mars were fossil evidence of prior erosive runoff from liquid water. They placed the events as recently as 1 MYA, but conceded the bursts could also include present day occurrences.
Figure 3 – Proposed fossilized water runoff channels. (MSSS/NASA)
In 1998, one
of a growing number of “independent researchers,” Byran Butcher, noticed
and published on the Internet a curious “dark area.” He casually suggested it might be “a coffee stain, water, or a shadow.”
[15]
In July 2000, the authors published a much
more specific model, based on an MOC image of an unusually dark, highly
elongated “stain” emanating from an exterior point source on a crater
wall, proposing that it was a current water flow consistent with the
model Malin and Edgett had put forth a few days earlier.
[16]
They quickly found numerous additional examples.
Figure 4 – Proposed point source liquid water burst image from MO4-00072 (MSSS/NASA)
Subsequent
to this, Palermo, England and Moore also found that surface “stains”
were inconsistent with aeolian features, mass wasting or other non-fluvial
processes.
[17]
At the suggestion of one of the authors (Hoagland),
Palermo et-al then proceeded to systematically map the locations of
these “seep” images relative to Mars surface coordinates, to see if
there was a global pattern to their distribution.
As a control, they also mapped randomly-selected “non-stain”
images until a representative and statistically valid sampling had been
completed.
Immediately, two striking global patterns emerged: both pointing to present day liquid water as a source of the “stains” or “seepages.” In the first pattern, the map showed that seepage images seem to appear preferentially near equatorial latitudes, mostly between 30 degrees North and South; none were found above 40 degrees North and South. This implies that the phenomenon is restricted to warmer areas of Mars, which would be expected if these were truly water flows. An equatorial pattern is also inconsistent with the “dust avalanche” model put forth by Malin and NASA as an explanation for these features. [18]
Figure 5 – Map showing flow image distribution.
The second, more
important pattern discovered was that the water flows seemed to cluster
preferentially around two pronounced geological features on the Martian
surface: the Tharsis and Arabia mantle uplifts (“bulges” -- Figure 5). The theoretical factors behind this second (and very pronounced)
bi-modal “stain” distribution pattern are the primary subjects of this
paper.
Mars as a Tidal Locked Moon of a Companion Body
The authors are proposing in this paper
that Mars, at some point earlier in solar system history, was captured
by one of two larger planetary bodies orbiting near the present day
orbit of Mars. This scenario
is an extension of the Capture Theory model of solar system formation
put forth by Dorman & Woolfson (1977), as well as Van Flandern’s
Exploded Planet Hypothesis (1978).
It is also based on current observations of significantly elliptical
orbits for many newly-discovered Extra Solar planets around nearby stars,
as reported by Butler, et-al.
[19]
One relevant example is the Jupiter-massed
planet orbiting the nearby K-type star, Epsilon Eridani. With an orbital period of 6.9 years, an orbital
eccentricity of 0.6, and an average distance from its star of 3.4 astronomical
units (AU), this planet’s orbit would take it as far out as Jupiter
and as close as Mars if it orbited in our own solar system.
[20]
It
is our proposal that two previous planets in the vast “gap” between
the current orbits of Jupiter and Mars, with orbital eccentricities
far less than the Epsilon Eridani planet, after several billion years
were gradually perturbed into a series of close encounters.
This eventually resulted in the low-probability but possible
“three-body capture” of a third object, the formerly freely orbiting
Mars, and millions of years later, the actual collision of the two larger
planets. As noted, such theoretical
former solar system members have been referred to as “Planet K” and
“Planet V” in Van Flandern’s original EPH model, the latter estimated
to possess approximately 4-5 Earth masses.
We
propose that, like theoretical models invoked now to explain some Extra
Solar System observations of formerly interacting planets,
[21]
a rare multi-planet encounter occurred late in solar
system history between two planets formerly occupying the current gap
between Jupiter and Mars: two massive terrestrial planets termed “K”
and “V.” As a result, Mars was robbed of a critical portion of its solar
angular momentum, allowing capture in an extreme elliptical orbit as
a new satellite of Planet V.
An
alternative scenario involves only one former solar system member –
Planet V.
Given
the parameters of existing solar system members -- distance, density,
and mass, especially Mars’ low density compared to the other terrestrial
planets (Figure 2) -- it seems reasonable to assume that if two additional
Earth-massed planets had formed between Jupiter and Mars, they would
have incorporated significantly more water than did Earth.
And, given the increased likelihood of multiple glancing collisions
in the early planetesimal phase for this region of the solar system,
[22]
they probably possessed multiple natural satellites
as well. An encounter of Mars with such a system, billions
of years after its formation (as we are proposing), would thus have
a reasonable probability of encountering a satellite as well. This type of encounter has a much higher probability of happening
than the previous scenario presented (the three-body interaction of
Planet K, Planet V, and Mars). But,
this second type of encounter could also result in Mars being captured
by Planet V – via the ejection of one of Planet V’s own moons. Calculations examining similar scenarios have been performed in
connection with the anomalous Neptune system – which consists now of
a major planet-sized satellite (Triton) in retrograde orbit, and a smaller
moon (Nereid) in a highly elliptical one.
This has been viewed for years as prima-facie evidence for a
highly unusual Neptune encounter earlier in solar system history with
an outside object in heliocentric orbit, which reversed Triton’s orbit
and ejected a previous moon from the system entirely.
That “escaped satellite” is now known as “Pluto.”
[23]
Figure 6 – Mars captured by the larger Planet V and brought into a tidal lock relationship, with gravitational bulges developing on opposite sides of Mars, 90 degrees to the spin axis of Planet V. Bulges precisely correspond to the Tharsis and Arabia bulges, 180 degrees apart.
Regardless of the precise methodology of capture, the subsequent, strong tidal relationship between Mars and the more massive Planet V (Figure 6) would have resulted in a further, rapid loss of Mars spin angular momentum, from a “free” rotation period in solar orbit on the order of ~12 hours down to the presently observed ~24. This estimate is based on models of Earth’s primordial rotation slowed by early lunar tides ( Figure 7). [24] In the model, inevitable tidal evolution not only ultimately circularized Mars orbit around Planet V, it resulted in Mars finally rotating/revolving around Planet V synchronously, in approximately 24 hours -- with one side always facing Planet V, as Earth’s Moon does today.
Figure 7 - Growth increments of fossils and tidal sediments on Earth record
a significantly shorter day as one moves further back in time.
It is the authors’
central proposal in this paper that it was this verifiable “Mars tidal
lock relationship” with Planet V that accounts for a host of previously
inexplicable and even contradictory Martian surface features, that otherwise
will remain perpetually mysterious.
This begins with the otherwise baffling present-day Tharsis and Arabia antipodal uplifts on the planet, which are located precisely 180 degrees opposite (Figures 8 and 9). In this tidal model, the Tharsis “bulge” -- a huge upwelling in the mantle and crust of Mars, unique in the solar system – is explained as a combination of the extended gravitational tidal influence of the larger Planet V acting for a significant period of time on that hemisphere, in concert with pre-existing internal mantle upwellings. As would be expected from such a tidal situation, a smaller but still significant “anti-bulge” would inevitably be raised at the antipodal location to Tharsis -- which accounts for the Arabia uplift precisely 180 degrees around the planet.
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All formerly fluid or partially fluid bodies in the solar system, including the inner moons of Jupiter and Saturn, show signs of such tidal evolution. Io, in particular, has significant bi-modal tidal bulges, similar to the model we are proposing now for Mars. [25] We additionally postulate that other heretofore inexplicable geologic features, such as Valles Marineris and the Elysium Mons, were also an extended result of this former tidal mechanism. The authors also propose that, when this tidal lock relationship was severed -- by the events directly leading to the destruction of Planet V -- Mars rotational polar axis obliquity, relative to the plane of its satellite orbit, dramatically shifted. This sudden obliquity shift, as part of this rapidly timed sequence of events, is responsible in the model for the apparent discrepancy of the “Line of Dichotomy” blast wave being inclined about 55 degrees to that rotational axis -- instead of being focused on the Tharsis region itself (see details, below).
Example of typical anti-podal tidal bulge on Earth
Original capture model and consequences
After capture, as this close orbital
relationship between Mars and Planet V evolved and the orbit circularized
over hundreds of thousands or even millions of years, any surface water
of oceanic volume would have “sloshed” back and forth across the surface
of Mars twice every Martian “day,” just as lunar tides do here on Earth. We assert, based on this intrinsic tidal process,
that Mars at the time of capture had to have been a “warm, wet world”
with both a denser atmosphere and a copious supply of flowing liquid
water, otherwise it would not evidence the major surface signatures
of tidal movement we will demonstrate.
But first: as an
intrinsic aspect of this model, we begin by proposing that the puzzling
“mantle uplift” of Tharsis began long before this dynamic capture sequence
culminated. Once Mars was captured
and oriented with the pre-capture “heavy side” (Tharsis) pointed “down”
(toward Planet V), the uplift process was then further and extensively
augmented by the “stretching” gravitational forces of Planet V close
by. Further, we suggest that this process resulted
in the relatively brittle crust of Mars weakening at the eastern base
of the now stretched Tharsis rise, resulting in a series of radial fissures
opening up – one of which was then radically enlarged to become the
Valles Marineris canyon system.
Figure 10 – A typical terrestrial tidal bore wave making its way up a river basin.
In the model, this original tension crack was inevitably expanded by the erosive effects of a massive volume of directed tidal waters – termed a “tidal bore” [26] (Figure 10) -- rushing back and forth (at several hundred kilometers per hour!) the entire ~ 1600 kilometer plus length of the original fissure, twice each Martian day, in direct response to the original spin rate of Mars and the massive gravitational tides caused by Planet V. Before Mars’ tidal lock with the larger planet was achieved, this enormous surge would have flowed, always westward, around the circumference of Mars in the direction opposite Mars spin, until it piled up against the immobile eastern side of the pre-capture Tharsis bulge. At that point, when “high tide” passed, the released waters would have rushed (under Mars gravity) back down the canyon system toward the east, scouring the floor once more, until the next “high tide.” This almost unimaginable force of rushing water, through an expanding canyon system of parallel fissures eventually opened up by the fluvial erosion, would have recurred twice each Martian “day,” possibly for several million years -- until Mars’ rotation was finally stationary relative to Planet V.
Figure 11 – Valles Marineris, a heretofore inexplicable trough extending one quarter of the circumference of Mars, is the largest canyon in the Solar System. The authors submit that this a fluvial trench generated by tidal bore action during Mars’ “captured satellite” phase.
It
is our proposal that this “scrubbing action” eventually resulted in
a radical deepening of the original narrow cleft to form the present
day ~7-km-deep, ~4000-km-long canyon system known as “Valles Marineris”
– a system (Figure 11) now stretching one quarter of the way around
the planet Mars.
This
assumes that Mars, like the other planets of the solar system, prior
to its capture had a prograde spin.
Thus, the tides induced by Planet V forced the rising and falling
waters to always assault the eastern side of Tharsis – which
is precisely where Valles Marineris formed.
The newly-found bi-modal clustering of “stains” (current water flows) exclusively in the Tharsis and Arabia regions of the planet by Palermo (2001), 180 degrees apart, is an additional major indicator that this model is correct. This accounts not only for tidal bi-modal crustal deformation of the planet, as predicted by the satellite model, but also implies that major quantities of unevenly distributed fluid (water) once also existed on the surface. Presumably, this water primarily resided after “tidal lock” in two opposing “tidal ocean bulges” – with possible dry land between -- because of the inevitable bi-lobed tidal forces experienced by Mars as an ultimately synchronously rotating satellite of Planet V.
The evidence argues that, once Mars lost its remaining spin momentum and established this stable