Olympus Mons may have once been an island on Mars

The huge Olympus Mons volcano on Mars—one of many photo voltaic system’s highest peaks—could have towered above a Martian ocean within the distant previous, a brand new examine suggests.

The analysis identifies an escarpment on the base of the large volcano that appears much like these discovered on volcanic islands right here on Earth, reminiscent of Hawaii and the Azores. These options are brought on when molten lava flows into the ocean, and the researchers argue that Olympus Mons could have fashioned a volcanic island roughly 3.8 billion years in the past.

Hawaii and Olympus Mons have “sort of an identical morphology, however Olympus Mons is far greater,” says volcanologist Anthony Hildenbrand of the French Nationwide Middle for Scientific Analysis. “By itself, Olympus Mons has greater than the full quantity of all of the Hawaiian island chain.”

Hildenbrand is the lead writer of the examine, which was revealed not too long ago in Earth and Planetary Science Letters. Along with the escarpment round Olympus Mons, Hildenbrand and his colleagues report indicators of an identical escarpment on one other Martian volcano, Alba Mons, which lies about 1000 miles to the northeast—suggesting this, too, was attributable to scorching lava flowing into the ocean.

However their claims are questioned by different consultants who counsel the escarpments may even have been made by lava flows that didn’t encounter water, forming terraces that have been a lot too excessive to be historical shorelines.

To handle this downside, the authors counsel what have been as soon as lava shorelines have been raised to their current top by volcanic uplift. However planetary scientist and geophysicist Patrick McGovern of the Lunar and Planetary Institute in Houston, who wasn’t concerned within the examine, says there’s no sign up information from NASA orbiters that this occurred.

“That type of factor would have a reasonably immense sign within the gravity area, and I actually can’t discern it within the gravity area information that we’ve,” he says.

Huge Martian volcano

Olympus Mons as we speak covers an space in regards to the dimension of Arizona. Scientists suppose it’s so huge as a result of the gravity on Mars is simply a couple of third of that on Earth and since the volcanic plume that created it has been very lively over the eons. Mars has no tectonic plates that would have moved the mountain away from this supply of magma, permitting it to develop and develop.

The volcano has by no means been seen to erupt, however research counsel it may need as not too long ago as two million years in the past—which suggests it may erupt once more.

Seen from above, Olympus Mons is roughly round, with huge overlapping craters from historical calderas seen on its peak—a defend volcano constructed up from layers of lava, like lots of Earth’s volcanic islands. The escarpment round its base is clearly seen on the northwest and southeast of the mountain, the place the slope all of a sudden plunges down for a number of miles.

“A plan view from the highest of Olympus Mons exhibits the escarpments are concave in direction of the middle,” Hildenbrand says. “And the sharp variations within the slope of about 15 levels are extremely in keeping with what we observe round terrestrial volcanic islands.”

He says that what are interpreted as historical shorelines in components of the northern highlands could possibly be proof of an ocean there within the distant previous, or perhaps two oceans at completely different occasions: the primary about 3.8 billion years in the past, and one other as not too long ago as three billion years in the past.

Different consultants are skeptical of this concept, nonetheless. The escarpments on Olympus Mons stretch roughly 4 miles above the encompassing plains—about twice the estimated most depth of the traditional ocean that’s thought to have as soon as crammed the northern hemisphere of Mars, the place the volcano is situated.

Geologist Julia Morgan of Rice College in Houston, who research the evolution of volcanic islands like Hawaii, says the escarpments may as an alternative be “benches” of lava that develop on the decrease flanks of volcanoes as a consequence of outward spreading as they develop, unrelated as to whether any shorelines are current.

Altering Martian landscapes

The authors of the examine counsel the escarpment fashioned at sea stage when Olympus Mons was decrease than it’s now, and that its current top was attributable to volcanic uplift.

“We don’t say that there was a world ocean that was six thousand meters deep,” Hildenbrand says. As a substitute, they counsel that the nice weight of the volcano pushed the encompassing seafloor down and that it rose once more with the later uplift.

He notes {that a} comparable escarpment on the north aspect of Alba Mons, which the authors suppose additionally could have been attributable to molten lava flowing into the ocean, is lower than three miles above the close by plain, decrease than the escarpment on Olympus Mons. In that case, it might be that the preliminary despair or the following uplift was not as nice, he says.

Alba Mons has very completely different construction than Olympus Mons. It’s comparatively flat—simply 4 miles excessive—however is surrounded by huge lava outflows that cowl an space virtually the dimensions of the USA.

It lies inside the northern volcanic highlands of the Tharsis area, whereas Olympus Mons stands other than them, within the west. That implies Alba Mons could not have been a whole island however a volcanic cape, Hildenbrand says.

Planetary volcanologist Lionel Wilson, a professor emeritus at Lancaster College in the UK, says the concept the cliffs round Olympus Mons have been fashioned by water has been proposed earlier than, however the nice top of the escarpment was not utterly defined. The brand new examine suggests Olympus Mons grew from volcanic uplift, however the authors want to search out extra proof of the sequence of occasions, he says.

McGovern provides that different geological processes may have created the escarpments as nicely, and he’s glad to see such questions being researched. “I’m not satisfied by the general situation,” he says. “But it surely’s an fascinating speculation … Olympus Mons is all the time fascinating to check.”

Future radiometric relationship on the rocks within the Olympus Mons escarpments may reveal precisely when and the way they fashioned. In the mean time their age can solely be estimated by finding out craters left by meteorite impacts throughout the area.

Hildenbrand hopes such rock samples could possibly be taken by future Mars probes, and both returned to Earth or remotely measured on the purple planet itself. “Then we may date with the precise numerical ages, relatively than not directly by crater counting,” he says. “Samples from these two volcanoes may present us the place the ocean was, and when it was.”


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