An SwRI-led team compared the early impact history of Venus and Earth, determining that Venus experienced higher-energy impacts creating a superheated core. Models show these conditions could create Venus' extended volcanism and younger surface. Credit: Southwest Research Institute
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Southwest Research Institute-led team has modeled the early impact history of
Venus to explain how Earth's sister planet has maintained a youthful surface
despite lacking plate tectonics. The team compared the early collision
histories of the two bodies and determined that Venus likely experienced
higher-speed, higher-energy impacts creating a superheated core that promoted
extended volcanism and resurfaced the planet.
"One of the mysteries of the inner
solar system is that, despite their similar size and bulk density, Earth and
Venus operate in strikingly distinct ways, particularly affecting the processes
that move materials through a planet," said Dr. Simone Marchi, lead author
of a new paper about these findings in Nature
Astronomy.
The Earth's shifting plates continuously
reshape its surface as chunks of the crust collides to form mountains ranges,
and in places promote volcanism. Venus has more volcanos than any other planet
in the solar system but has only one continuous plate for its surface. More
than 80,000 volcanos—60 times more than Earth—have played a major role in
renewing the planet's surface through floods of lava, which may continue to
this day. Previous simulations struggled to create scenarios to support this
level of volcanism.
"Our latest models show that
long-lived volcanism driven by early, energetic collisions on Venus offer a
compelling explanation for its young surface age," said Professor Jun
Korenaga, a co-author from Yale University. "This massive volcanic
activity is fueled by a superheated core, resulting in vigorous internal melting."
This high resolution (1 million particles)
computer simulation illustrates an 1,800-mile-diameter (3,000-kilometer)
projectile striking Venus head-on at 18 miles per second (30 km/s). On the
left, the colors indicate different materials — brown for Venus' core; white
for the projectile's core; and green for the silicate mantle of both objects.
The colors on right side indicate the temperature of the materials. Credit:
Southwest Research Institute
Earth and Venus formed in the same
neighborhood of the solar system as solid materials collided with each other and gradually combined
to form the two rocky planets. The slight differences in the planets' distances
from the sun changed their impact histories, particularly the number and
outcome of these events.
These differences arise because
Venus is closer to the sun and moves faster around it, energizing impact
conditions. In addition, the tail of collisional growth is typically dominated
by impactors originating from beyond Earth's orbit that require higher orbital
eccentricities to collide with Venus rather than Earth, resulting in more
powerful impacts.
"Higher impact velocities melt
more silicate, melting as much as 82% of Venus' mantle," said Dr. Raluca
Rufu, a Sagan Fellow and SwRI co-author. "This produces a mixed mantle of
molten materials redistributed globally and a superheated core."
A Southwest Research Institute-led team has
modeled the early impact history of Venus to explain how Earth's sister planet
has maintained a youthful surface despite lacking plate tectonics. The new
model suggests that the planets' distances from the Sun resulted in higher-energy,
higher-velocity impacts to Venus. These powerful collisions created a
superheated core that promoted extended, extensive volcanism and resurfaced the
planet. Credit: Southwest Research Institute
If impacts on Venus had
significantly higher velocity than on Earth, a few large impacts could have had
drastically different outcomes, with important implications for the subsequent
geophysical evolution. The multidisciplinary team combined expertise in
large-scale collision modeling and geodynamic processes to assess the
consequences of those collisions for the long-term evolution of Venus.
"Venus internal conditions are
not well known, and before considering the role of energetic impacts,
geodynamical models required special conditions to achieve the massive
volcanism we see at Venus," Korenaga said. "Once you input energetic
impact scenarios into the model, it easily comes up with the extensive and
extended volcanism without really tweaking the parameters."
And the timing of this new
explanation is serendipitous. In 2021, NASA committed to two new Venus
missions, VERITAS and DAVINCI, while the European Space Agency is planning one
called EnVision.
"Interest in Venus is high
right now," Marchi said. "These findings will have synergy with the
upcoming missions, and the mission data could help confirm the findings."
by Southwest Research Institute
Source: Researchers find ancient, high-energy impacts could have fueled Venus volcanism (phys.org)
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