Spacecraft Searching for Remains of Mystery Planet

Article written: 10 Apr , 2009
Updated: 24 Dec , 2015


How did our Moon form? The leading hypothesis, the Giant Impact Theory, proposes that in the formative years of the Solar System, a Mars-sized protoplanet crashed into Earth. Debris from the collision, a mixture of material from both bodies, spun out into Earth orbit and coalesced into the Moon. Soon, this theory will be tested, perhaps answering the question of how our Moon was born. Two identical NASA spacecraft are preparing to enter areas in space known as the Lagrangian points where remains of this mystery protoplanet may be hiding. The spacecraft duo, called Solar Terrestrial Relations Observatory, or Stereo, will pass by the L4 and L5 points where the gravity of the sun and Earth combine to form gravitational wells where asteroids and space dust tend to gather.

During their journey, the two spacecraft will use a wide-field-of-view telescope to look for asteroids orbiting the region. Scientists will be able to identify if a dot of light is an asteroid because it will shift its position against stars in the background as it moves in its orbit.

The Giant Impact Theory explains many aspects of lunar geology including the size of the Moon’s core and the density and isotopic composition of moon rocks. A modification of the Giant Impact Theory is the “Theia hypothesis,” a brainchild of Princeton theorists Edward Belbruno and Richard Gott.

“About 4.5 billion years ago when the planets were still growing,” said Michael Kaiser, Stereo project scientist at Goddard Space Flight Center, “a hypothetical world called Theia may have been nudged out of L4 or L5 by the increasing gravity of other developing planets like Venus, sending it on a collision course with Earth. The resulting impact blasted the outer layers of Theia and Earth into orbit, which eventually coalesced under their own gravity to form the moon.”

The 18th-century mathematician Joseph-Louis Lagrange realized there were five such wells in the sun-Earth system. The twin probes are approaching L4 and L5.

“These points may hold small asteroids, which could be leftovers from a Mars-sized planet that formed billions of years ago,” said Kaiser.

Deployment of STEREO Spacecraft Panels. Credit: 2002-Johns Hopkins University Applied Physics Laboratory. Credit: Dr C.J.Eyles, University of Birmingham

Deployment of STEREO Spacecraft Panels. Credit: 2002-Johns Hopkins University Applied Physics Laboratory. Credit: Dr C.J.Eyles, University of Birmingham

The theory explains puzzling properties of the moon, such as its relatively small iron core. At the time of the giant impact, Theia and Earth would have been large enough to be molten, enabling heavier elements, like iron, to sink to the center to form their cores. An impact would have stripped away the outer layers of the two worlds, containing mostly lighter elements like silicon. The moon eventually formed from this material.

Stereo’s primary mission is to give three-dimensional views of space weather by observing the sun from the two points where the spacecraft are located. Images and other data are then combined for study and analysis. Space weather produces disturbances in electromagnetic fields on Earth that can induce extreme currents in wires, disrupting power lines and causing wide-spread blackouts. It also can affect communications and navigation systems. Space weather has been recognized as causing problems with new technology since the invention of the telegraph in the 19th century.

Sources: Goddard Space Flight Center, [email protected]

18 Responses

  1. Cosmic Force says

    Perhaps the asteroid belt and our moon is the aftermath of this collision.

  2. Jon Hanford says

    L4 and L5 positions have been extensively searched by a variety of very sensitive earth-bound cameras back in the late 50’s & early 60’s. No clouds of particles or individual objects were ever spotted at these locations. Of course these probes have the advantage of proximity and drastically improved detectors to conduct their survey, so I will be watching for the results when they appear.

  3. Amund Helland says

    I have 100 krone in a bet on this that they will find nothing at all!

  4. nibiru says

    Planet X, someone had to say it.

    Amund Helland
    I have 50 øre on them finding it and 10 on them telling us about it if it poses a threat.

  5. Statitistically the leading hypothesis in science is always wrong.

    “In young scientific fields, if you say all the adopted positions are wrong, you’ll seldom be wrong.” — Jeremiah P. Ostriker, cosmologist, 1996

    So we can safely discard the Giant Impact Hypothesis in favor of the less popular capture hypothesis.

    “…the pre-Hellenic Pelasgian inhabitants of Arcadia called themselves Proselenes, because they boasted that they came into the country before the Moon accompanied the Earth. Pre-Hellenic and pre-lunarian were synonymous.” — Alexander Von Humboldt, geologist, 1851

    “‘The stars did not yet revolve in the heavens; the Danaides had not yet appeared, nor the race of Deucalion; the Arcadians alone existed, those of whom it is said that they lived before the Moon, eating acorns upon the mountains.” — Apollonios Rhodios, librarian, ~246 B.C.

  6. Neil says

    Oills: you are one weird dude.

  7. Ben Shelef says

    yeah oils, evidence of tidal pools is probable older then written history… unless of course history only began with the invention of electricity, and older artifacts are simply temporal reflections off of the neutralino-plasma barrier that was formed by the spontaneous formation of the magnetic monopole adhesion layer that separates the positive and negative pseudo-hemispheres that make up the conjugate charge matter cloud that we mistakenly call the space time continuum.

    (takes deep breath)

  8. zibit says

    I’d be more inclined to listen to EU theory if the only people who promote it weren’t absolutely bonkers.

  9. star grazer says

    Jon Hanford Says
    Interesting about your reports of Earth bound survey
    in the late 50s’ and 60′. I believe there may be a swarm of small rocky fragments in those L4-L5 regions . These rocky fragments escaped detection because they are very small and none posts any threat to Earth. However, I’m with you on watching for the results.

  10. Jon Hanford says

    Yeah. Think the earlier searches used surplus Aero-Ektar lenses and Baker-Nunn Schmidt cameras probably on grainy IIa-D film or plates to capture the yellow portion of the spectrum where these particles had the best S/N ratio.

  11. Essel says

    Detection of Asteroids or debris in L4 and L5 is fine but how do we detect the composition of such left over material and prove that the debris are indeed unique and from the mars sized impactor?

    What are the capabilities of STEREO to detect the rock composition?

  12. Jon Hanford says

    Oillsmastery quotes JP Ostriker (1996): “In young scientific fields, if you say all the adopted positions are wrong, you’ll seldom be wrong.” Then may I posit Plasma Cosmology, Electric Cosmology, Plasma Universe, Electric Universe, Anti-Gravity Matter and Aether Wave Theory are ALL wrong.

  13. star grazer says

    Essel Says
    I really doubt there are any debris left from the impact, although I believe there are small rocky framents from much later rocks that got into the L4-L5 areas. I would think after 4 billion years, large comets went through the L4,L5 areas and ‘hi-jacked’ or set these ‘smoking gun’ rocks in a trajectory towards the Sun and slinged out the Solar System and some are headed out of the Milky Way galaxy and the others, who know where…….. The tiny rocks I think are now in the L4-L5 areas will remain there until another large comet gets close and send them whereever.,according to ones’ imagination.

  14. Jon Hanford says

    @ Ben Shelef: I couldn’t have said it better myself….’cause it makes absolutely no sense, like some of our brethren here! Your post is probably going into some ‘quote’ folder that seems popular with some of these misguided alt-science people. @ Essel: STEREO is a mission primarily devoted to solar observations. As such, no spectrometer or other spectral analysis equipment is included with the probe. Use of an UV imager may be the only instrument on board with even a (slim) chance of running across something at the Lagrangian points. See a detailed list of experiments on STEREO here: .

  15. solrey says

    Apparently there is also an electromagnetic component to the Lagrangian points, as indicated in the abstract linked below.

    “In addition, the ACE/SWEPAM instrument identifies IMF connection between the L1 point and the Earth’s bow shock by the presence of low-energy (272-372 eV) bi-directional electron flux.”

    Bi-directional electron flux. Could this be caused by a rotating magnetic field within the L1 point?
    “Electron flux” is another way to say electric current.

    “We find similar distributions of radial and non-radial IMF orientations both close to the bow shock and at L1. This implies that the IMF configurations during upstream events are large-scale spatial structures with radii of curvature on the order of the Earth-L1 distance, i.e. 0.01 AU. These spatial structures are being convected through the L1 point into the Earth’s foreshock.”

  16. solrey says

    This is intriguing. A ‘motor’ that uses gravity and magnetism, and the magnets are oriented nearly identical to the Lagrangian points. Compare the diagram in this article to the diagram in the following link:

  17. Feenixx says

    solrey says:
    “This is intriguing. A ‘motor’ that uses gravity and magnetism, and the magnets are oriented nearly identical to the Lagrangian points.”

    I reckon: the first motor of this kind was invented in the 8th century in India, by the astronomer Lalla. This has been followed by dozens more, right up to the present day, based on the same principle: an off-centre wheel with weights shifting as it rotates to re-balance it.
    Magnetism has nothing to do with the motion of this motor. The magnets hold the parts in position. Gravity is supposed to drive it.
    Motors like this simply don’t work. Whichever way you position the wheel, the weights will shift to restore equilibrium. The stored (potential) energy is the same for all rotational positions.

    and then, solrey recommends:
    “Compare the diagram in this article to the diagram in the following link…”

    I compared, and came to the conclusion: Conceptionally, these two diagrams have nothing to do with each other. It’s just that the pictures look similar.

  18. Jon Hanford says

    @solrey: Why not give us a link to the page noted in your last post (see the Andy Gravity-Magnet Motor page here: ? It has a lot of pretty pictures with captions, too! Might be a little advanced for 5th to 8th graders, but maybe solrey can figure a little of it out. My fav on the page is the perpetual motion machine (cut to video). Just look at the ‘Tesla inspired ‘ site hosting this page – Pure Energy Systems Wiki (PESWiki). This must be the place cranks barred from contributing at Wikipedia go to rant on ( I’ve already suggested EU/PC/PU/EC adherents here at UT consider posting elsewhere where they can be taken more “seriously” by their peers ).

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