Earth’s strange blobs could be huge pieces of alien planet

The video discusses the impact of a planet-sized body called Thea on Earth around 4.5 billion years ago. Scientists theorize that Thea's remains formed two large, mysterious blobs of rock deep in Earth's mantle. These blobs, located beneath West Africa and the Pacific Ocean, are dense and chemically distinct from surrounding mantle rock. Seismologists have studied these formations for decades, and new isotopic evidence suggests they may be remnants of Thea. The study is currently under review.

What evidence suggests that the blobs in the mantle are denser and chemically different?

What does Ren believe about the blobs based on new isotopic evidence?