{"id":32765,"date":"2023-09-02T09:00:00","date_gmt":"2023-09-02T07:00:00","guid":{"rendered":"http:\/\/3ac53357-29ff-4d7b-87af-89b62ed918a0"},"modified":"2023-09-02T09:46:13","modified_gmt":"2023-09-02T07:46:13","slug":"why-even-a-tiny-asteroid-could-knock-earth-out-of-orbit","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/rss_feed\/why-even-a-tiny-asteroid-could-knock-earth-out-of-orbit\/","title":{"rendered":"Why even a tiny asteroid could knock Earth out of orbit"},"content":{"rendered":"

The impact an asteroid could have on Earth depends on many things including velocity, angle and geology. <\/p>

By Dr Alastair Gunn\n <\/p>

Published: Saturday, 02 September 2023 at 07:00 AM<\/p>

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Theoretically, any two objects\u00a0colliding with\u00a0each other will involve a transfer of momentum that alters their trajectories. So, even a micrometeorite, weighing\u00a0less than\u00a0a gram, could result in an imperceptible change\u00a0in\u00a0Earth\u2019s\u00a0orbit around the Sun<\/a>. However, things are not quite that simple.\u00a0<\/p>

Generally, the larger the impacting object the larger the effect of its impact. But the effect depends on many things, for example:\u00a0the density and tensile strength of the impactor;\u00a0the geology of the impact point; and the angle and velocity of the impact.\u00a0<\/p>

Crucially though, the transfer of momentum to Earth during an impact is far from total. This is because the impactor is often fractured or vaporised prior to hitting Earth\u2019s surface.<\/p>

The large kinetic energy of the impactor is converted mostly to heat (due to friction as it travels through\u00a0Earth\u2019s\u00a0atmosphere) and only a small amount is felt as mechanical energy. Even this small amount of mechanical energy goes mostly into deforming and fracturing Earth\u2019s surface and destroying the impactor. Almost none of the impactor\u2019s energy ends up changing Earth\u2019s momentum.<\/p>

Scientists are aware of numerous large impact sites that survive on\u00a0Earth\u2019s\u00a0surface. The largest, Vredefort Crater in South Africa,\u00a0implies an object about 20km in size, travelling at up to 90,000 km\/h, hitting Earth about 2 billion years ago. That object was probably just 100-millionth of the mass of Earth. This huge mass difference, and the fact that very little momentum is transferred, implies that no known impact event has significantly altered Earth\u2019s orbit.\u00a0<\/p>

This doesn\u2019t mean that these impact events are without consequences. Most are associated with mass extinction events, such as the Chicxulub event<\/a>,\u00a0which accounts for the demise of the dinosaurs. Their immediate effect is to completely vaporise anything in their vicinity\u00a0and\u00a0perhaps create mega-tsunamis, earthquakes and volcanism.<\/p>

They\u2019re also thought to result in significant changes to Earth\u2019s atmosphere and the global climate. But what they don\u2019t do is throw Earth out of its orbit.\u00a0<\/p>

However, things were different in the Solar System\u2019s\u00a0early\u00a0history. Then, there were many more and much larger objects capable of impacting the infant planets. It\u2019s widely believed that the Moon is the result of a catastrophic impact with the primitive Earth. The orientation of Uranus\u2019s\u00a0rotation axis (almost perpendicular to its orbital plane) suggests that an Earth-sized object crashed into\u00a0it 3 to 4 billion years ago.<\/p>

These kinds of impacts, where the impactor\u2019s mass is a significant fraction of the planet\u2019s mass, would certainly have been powerful enough to alter their orbits. So, it\u2019s probably safe to say that all the planets of the Solar System have had their orbits altered by impacts. Exactly when, how and by what is, unfortunately, impossible to say.\u00a0<\/p>

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