Moon’s Mysterious Tilt Finally Explained

The moon had been a presence in the Earth's skies for as long as history knows, but the mysterious tilt of its orbit has always puzzled scientists - until now.

Space.com reported that the mysterious tilt may now have an explanation, and it comes from an angled, giant impact that vaporized most of the Earth in prehistoric times. The same impact may have even created the moon in the process. To take note, the moon's orbit it slightly inclined compared to the Earth's around the sun by a mere 5 degrees, but scientists were never able to find a theory regarding the said tilt until now.

Research suggested that in the early days of the formation of the planets, the Earth, then newborn, grazed a rock the size of Mars, called Theia. Debris from the impact then became our own planet's satellite.

The giant-impact hypothesis explained many of the details regarding the moon and the earth, including the size of the satellite compared to the Earth, and the rotation rates of both bodies - however, it seemed that in the last decade and a half, new evidence challenged the theory and led them to rework the details.

Scientists discovered that terrestrial and lunar rocks had more in common than expected - so the latest version of the giant-impact hypothesized that an "extraordinarily high-energy impact" helped make the moon - it is so violent that it vaporized not only Theia but also most of the Earth, leaving behind only the mantle region. Kaveh Pahlevan and Alessandro Morbidelli also noted in Phys.org that no single object could be strong enough to yank the moon out of its expected orbit - so before the said high-impact event, it is likely that the gravity of many objects combined managed to do so.

The dense vapor then formed a cloud 500 times larger than today's Earth, and most of the material fell back on the planet as it cooled - while the rest went on to form the moon.