Deep inside Earth, far below the crust and mantle we learn about in school, two colossal structures loom above the core like buried continents. New research argues these dense, mysterious formations may be the surviving pieces of a molten protoplanet that slammed into the young Earth, leaving behind a planetary scar that still shapes our world today. If that idea holds, the blobs are not just a curiosity of geophysics, but a fossil record of a violent collision that may also be tied to the birth of the Moon.
I want to unpack how scientists even know these hidden giants exist, why some researchers now suspect an ancient world is entombed inside our own, and what that means for everything from volcanic hot spots to the long-term evolution of Earth’s interior. The story is still unfolding, and several details remain unverified based on available sources, but the emerging picture is one of a planet whose deepest secrets are anything but settled.
What scientists actually mean by “two vast blobs”
When geophysicists talk about the blobs, they are not picturing tidy spheres or cartoonish lumps. They are referring to two sprawling regions of unusually dense, slow-moving mantle material that sit just above the core, one beneath Africa and the other beneath the Pacific. Seismic waves from earthquakes travel more slowly through these zones than through surrounding rock, which is how researchers first mapped their outlines and realized they were distinct from the rest of the lower mantle. In some visualizations, these structures are described as “large low-shear-velocity provinces,” but the shorthand of giant blobs has stuck because it captures both their scale and their strangeness.
These deep anomalies are so massive that some scientists liken them to hidden continents, each thousands of kilometers across and rising hundreds of kilometers above the core–mantle boundary. Their presence has become one of the most striking internal oddities of our planet, a fact often highlighted in public explainers that describe them as two dense, gigantic regions perched above Earth’s core and mapped through global seismic networks, as in one widely shared visual overview. The key point is that these are not small anomalies or local quirks; they are planet-scale features that any complete model of Earth’s interior must account for.
How we discovered hidden “continents” above the core
The blobs emerged from decades of work in seismic tomography, a technique that uses earthquake waves to build three-dimensional images of Earth’s interior in much the same way a CT scan reconstructs the inside of a human body. As global seismic networks expanded and computing power grew, researchers began to see consistent patterns: two vast regions at the base of the mantle where shear waves slowed dramatically, signaling hotter or compositionally different material. Over time, these patterns sharpened into the outlines of the African and Pacific anomalies, convincing many geophysicists that they were not artifacts of limited data but robust features of the deep Earth.
Recent coverage has emphasized that these structures are now understood as “massive continents” of dense rock perched above the core, with some scientists arguing they could be remnants of a lost molten world that collided with Earth early in its history. That idea is laid out in reporting that describes how two such continents have been identified and modeled as potential traces of a protoplanetary impactor, a scenario explored in detail in analyses of two massive continents buried deep inside the planet. The discovery story is not a single eureka moment, but a slow convergence of seismic evidence that forced scientists to accept that Earth’s lower mantle is far from uniform.
Why these deep structures are so puzzling
Once the blobs were mapped, the obvious question followed: what are they made of, and why are they there? Their density appears higher than the surrounding mantle, and their seismic signature suggests a different composition, not just hotter rock. That has led to competing interpretations. Some researchers argue they are piles of subducted oceanic crust that have sunk all the way to the base of the mantle and accumulated over billions of years. Others see them as chemically distinct reservoirs that formed early in Earth’s history and have remained relatively isolated ever since, perhaps preserving primordial material from the planet’s formation.
The puzzle is sharpened by the way these structures interact with mantle plumes and surface volcanism. Many hot spots, including those that feed chains like Hawaii and Iceland, appear to be rooted near the edges of the blobs, hinting that the anomalies may help organize the flow of heat and material from the core to the surface. Coverage of the ongoing debate notes that scientists are still trying to explain why these regions are so sharply defined and why they seem to anchor deep upwellings that shape surface geology, a tension highlighted in reporting on how Earth’s blobs challenge standard models of mantle convection. The fact that such large, dense features persist without simply sinking into the core or dispersing into the mantle is one of the main reasons they remain an active research frontier.
The bold idea: a buried protoplanet inside Earth
Into this long-running mystery, a provocative hypothesis has gained traction: the blobs might be the surviving mantle of a protoplanet that slammed into the early Earth. In this scenario, a Mars-sized body, often associated with the theorized impact that formed the Moon, did not simply vaporize or merge uniformly with Earth. Instead, its denser mantle fragments sank toward the core and pooled into two giant reservoirs that we now detect as the African and Pacific anomalies. This would make the blobs literal planetary remains, a kind of internal fossil of a world that no longer exists on its own.
Supporters of this idea point to modeling work that shows how a high-energy collision could inject chemically distinct material deep into Earth’s mantle, where it would gradually settle into large, dense piles. Reporting on the new research explains that these piles could match the size and density of the observed blobs, suggesting they are not random features but the long-term outcome of a specific impact event. One detailed breakdown describes how the two strange giant blobs may finally be explained as the remnants of a molten protoplanet that collided with Earth, an argument laid out in coverage of two strange giant blobs deep inside the planet. While not all experts are convinced, the hypothesis offers a unifying story that links the blobs, the Moon’s origin, and the early chaos of the inner solar system.
How the “lost molten world” theory connects to the Moon
The idea that a protoplanet hit Earth is not new; it is central to the widely discussed giant impact hypothesis for the Moon’s formation. In that framework, a body sometimes called Theia struck the proto-Earth, ejecting material that eventually coalesced into the Moon. What is new is the suggestion that the impactor’s mantle did not fully mix with Earth’s, but instead survived as dense, chemically distinct reservoirs at the base of the mantle. If true, the blobs would be the hidden counterpart to the Moon, the part of the collision that never left.
Analyses of the new modeling work emphasize that the density contrast and spatial distribution of the blobs are consistent with what would be expected if fragments of an impactor’s mantle sank and pooled near the core. Some coverage frames this as a way to reconcile geochemical clues from lunar samples with the seismic picture of Earth’s interior, arguing that both may be recording the same ancient collision from different vantage points. One in-depth explainer even plays with the notion that these mysterious blobs could be the remains of an “alien planet” embedded in Earth’s mantle, a phrase used to capture the idea that they originated as part of a separate world, as discussed in a detailed look at two mysterious blobs that might trace back to a planetary impactor. The Moon, in this view, is only half the story; the rest is still glowing faintly at the base of our mantle.
What the blobs might be doing to Earth’s surface today
Even if the blobs began as impactor remnants, their influence would not be confined to deep time. Their presence appears to shape how heat and material move from the core to the surface, with consequences for volcanism, plate tectonics, and perhaps even the long-term stability of Earth’s magnetic field. Many mantle plumes that feed persistent volcanic hot spots seem to originate near the edges of the blobs, suggesting that these dense regions act as anchors or boundaries that guide rising columns of hot rock. That could help explain why certain regions, like the central Pacific and parts of Africa, have long histories of intense volcanic and tectonic activity.
Some reporting highlights that the blobs may be linked to large igneous provinces and supervolcanic events in Earth’s past, implying that their configuration could modulate the timing and location of major eruptions. Other coverage notes that the anomalies might influence how heat flows out of the core, which in turn affects the geodynamo that generates Earth’s magnetic field. While many of these connections remain active areas of research and some details are unverified based on available sources, the emerging consensus is that the blobs are not passive lumps but dynamic players in the deep Earth system, a point underscored in analyses that describe how these Earth blobs puzzle scientists precisely because they appear to interact with processes all the way up to the surface.
How scientists visualize a world we can’t visit
Because no probe can survive the journey to the core–mantle boundary, scientists rely on indirect methods and creative visualization to make sense of the blobs. Seismic tomography provides the raw data, but turning that into intuitive images requires careful modeling and, increasingly, sophisticated graphics. Researchers build three-dimensional renderings that show the blobs as towering structures rising from the core, often color-coded to indicate slower seismic velocities or higher densities. These visualizations help both scientists and the public grasp the sheer scale of the anomalies and their relationship to surface features like continents and ocean basins.
Public-facing explainers and social media posts have amplified these images, turning the blobs into a kind of underground iconography. Some posts show stylized cross-sections of Earth with bright red or orange masses under Africa and the Pacific, while others animate how seismic waves bend and slow as they pass through the anomalies. One widely shared video walkthrough uses animations and expert commentary to guide viewers through the evidence for the blobs and the new impactor hypothesis, as seen in a detailed video explanation that traces how seismic data and computer models converge on the idea of deep, dense structures above the core. These visual tools are not just educational; they also shape how scientists themselves think about the geometry and evolution of the blobs.
Why the “alien planet” framing both helps and misleads
As the impactor hypothesis has gained attention, some coverage has leaned into dramatic language, describing the blobs as the remains of an alien planet hidden inside Earth. That framing captures the genuine shock value of the idea that our world might contain the buried mantle of another, but it can also blur important scientific nuances. The protoplanet in question would have formed from the same basic building blocks as Earth, within the same young solar system, so in a strict sense it was not alien in the way a distant exoplanet might be. The real novelty lies in the notion that planetary collisions can leave long-lived, structurally coherent remnants inside the bodies they strike.
Still, the metaphor has power, especially when paired with striking imagery and accessible explanations. Social media posts and short videos often use the alien-planet hook to draw viewers into a more detailed discussion of seismic data, mantle convection, and planetary formation. One such post, for example, pairs a vivid graphic of Earth’s interior with a concise summary of the idea that deep blobs may be the remains of a molten world, as seen in a widely circulated visual summary that frames the blobs as planetary leftovers. The challenge for scientists and communicators is to harness that attention without overselling how settled the hypothesis really is, especially given that alternative explanations remain on the table.
What comes next in the hunt for Earth’s buried past
The next phase of research will likely focus on tightening the links between seismic observations, geochemical evidence, and impact modeling. On the seismic side, denser networks and improved algorithms should refine the shape and internal structure of the blobs, revealing whether they are homogeneous piles or layered, patchy reservoirs. On the geochemical side, scientists will keep probing volcanic rocks that may carry signatures of deep mantle material, looking for isotopic fingerprints that match what would be expected from an impactor’s mantle. If those lines of evidence converge, the case for a buried protoplanet will grow stronger; if they diverge, researchers may need to rethink the story.
Public interest in the blobs is likely to remain high, fueled by ongoing coverage and new explainer videos that revisit the topic as fresh studies appear. Some recent pieces have already highlighted how the two deep objects appear to be changing over geological time, suggesting that they may be slowly reshaping Earth’s interior in ways we are only beginning to understand, a theme explored in reporting on how two objects beneath the crust could be evolving. Other explainers, including accessible video breakdowns of the latest models, continue to walk viewers through the evidence and open questions, as in a popular deep-dive video that revisits the blobs in light of new simulations. For now, the safest conclusion is that Earth’s interior still holds surprises, and that the two vast blobs above the core may be our most tangible link to the violent, molten world that existed before our planet settled into its current form.
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