This causes an ongoing cycle in which new skin cells move to the outermost layer of skin too quickly in days rather than weeks.

CNN: Psoriasis

When the sun is relatively inactive as it has been in recent years the outermost layer of Earth's atmosphere cools dramatically, new observations find.

MSN: Earth's upper atmosphere cooling dramatically

The outermost part of this layer prevents other particles, like dirt and grime, from binding to it.

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