North Polar Basin (Mars)
Location | Northern Hemisphere, Mars |
---|---|
Coordinates | 67°N 208°E / 67°N 208°E |
The North Polar Basin, more commonly known as the Borealis Basin, is a large basin in the northern hemisphere of Mars that covers 40% of the planet.[1][2] Some scientists have postulated that the basin formed during the impact of a single, large body roughly 2% of the mass of Mars, having a diameter of about 1,900 km (1,200 miles) early in the history of Mars, around 4.5 billion years ago.[1][3] However, the basin is not currently recognized as an impact basin by the IAU. The basin is one of the flattest areas in the Solar System, and has an elliptical shape.[1][2]
Large regions within the Borealis Basin
Because the Borealis basin covers 40% of the surface of Mars, and much of the Northern Hemisphere, many currently recognized regions of Mars lie within it:[2]
Borealis Impact
Formation of the Borealis Basin
One possible explanation for the basin's low, flat and relatively crater-free topography is that the basin was formed by a single large impact. Two simulations of a possible impact sketched a profile for the collision: low velocity—6 to 10 km (3.7 to 6.2 mi) per second—oblique angle and a diameter of 1,600–2,700 km (990–1,680 mi).
This impact would have resulted in significant crustal melting and a general increase in the rate of crustal formation for a period of 40 million years following the impact.[7] Such a large impact would have disturbed the mantle, altering the normal convection currents and causing upwellings which further increase the amount of melting at the impact site.[7] Overall, such an event would actually increase the rate of cooling of the Martian interior.[7] The lack of magnetic anomalies observed in the northern hemisphere could be explained by such an impact, as the shock waves produced might have demagnetized the crust.[7]
Potential formation of Phobos and Deimos via Borealis impact
The origin of Mars' moons, Phobos and Deimos (pictured right), is unknown and remains controversial. One theory is that the moons are captured asteroids. However, the moons' near circular orbits and low inclination relative to the Martian equator are not in agreement with the capture hypothesis.[8] The detection of minerals on Phobos similar to those in the Martian lithosphere, and the unusually low density and high porosity of Phobos, such that the moon would not be expected to remain aggregate if dynamically captured, suggest that the moons could have formed via accretion in Martian orbit, similar to how Earth's Moon formed.[8]
While estimates of the mass ejected by a large, Borealis-size impact vary, simulations suggest that a body approximately 0.02 Mars masses (~0.002 Earth Masses) in size is capable of producing a sizable debris disk in Martian orbit, on the order of 5×1020 kg, with a significant fraction of the material remaining close to Mars.[3][8] This figure lies within the estimated mass range necessary to form the two moons, as other data suggests that only 1% of the mass of an accretion disk successfully forms moons.[8] There are several other large impact basins on Mars that could have ejected enough debris to form the moons.[8]
Ancient tsunamis
Analysis of Mars Global Surveyor data found mineral deposits similar to
See also
- Arctic Basin (Earth's "North Polar Basin")
- Mars ocean hypothesis(Oceanus Borealis)
- Planum Boreum
- Utopia Planitia
- Vastitas Borealis
References
- Martel, L.M.V. (June, 2001), "Outflow Channels May Make a Case for a Bygone Ocean on Mars", Planetary Science Research Discoveries. (retrieved 17 August 2005)
- ^ a b c "NASA - NASA Spacecraft Reveal Largest Crater in Solar System". www.nasa.gov. Retrieved 2017-04-06.
- ^ S2CID 1981671.
- ^ S2CID 4328610.
- S2CID 4402065.
- ^ "Huge Impact Created Mars' Split Personality". Space.com. Retrieved 2008-07-01.
- ^ Chandler, David (2008-06-25). "Solar system's biggest impact scar discovered: MIT scientists solve riddle of Mars' two-faced nature". MIT News. Retrieved 2015-01-01.
- ^ .
- ^ S2CID 17089080.
- ^ S2CID 132378050.