It is now a well-understood
fact that Mars once had quite a bit of liquid water on its surface. In fact,
according to a recent estimate, a large sea in Mars’ southern hemisphere once
held almost 10 times as much water as all of North America’s Great Lakes
combined. This sea existed roughly 3.7 billion years ago, and was located in
the region known today as the Eridania basin.
However, a new study based
on data from NASA’s Mars Reconnaissance Orbiter (MRO) detected vast mineral
deposits at the bottom of this basin, which could be seen as evidence of
ancient hot springs. Since this type of hydrothermal activity is believed to be
responsible for the emergence of life on Earth, these results could indicate
that this basin once hosted life as well.
The study, titled “Ancient
Hydrothermal Seafloor Deposits in Eridania Basin on Mars“, just recently
appeared in the most prestigious scientific journal Nature Communications. The
study was officially led by Joseph Michalski of the Department of Earth
Sciences and Laboratory for Space Research at the University of Hong Kong,
along with researchers from the Planetary Science Institute, the Natural
History Museum in London, and NASA’s Johnson Space Center.
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| The Eridania basin of southern Mars is believed to have held a sea about 3.7 billion years ago, with seafloor deposits likely resulting from underwater hydrothermal activity. Credit: NASA |
Together, this international
team used data obtained by the MRO’s Compact Reconnaissance Spectrometer for
Mars (CRISM). Since the MRO reached Mars in 2006, this instrument has been used
extensively to search for evidence of mineral residues that form in the
presence of water. In this respect, CRISM was essential for documenting how
lakes, ponds and rivers once existed on the surface of Mars.
In this case, it identified
massive mineral deposits within Mars’ Eridania basin, which lies in a region
that has some of the Red Planet’s most ancient exposed crust. The discovery is
expected to be a major focal point for scientists seeking to characterize Mars’
once-warm and wet environment. As Paul Niles of NASA’s Johnson Space Center
said in a recent NASA press statement:
“Even if we never find
evidence that there’s been life on Mars, this site can tell us about the type
of environment where life may have begun on Earth. Volcanic activity combined
with standing water provided conditions that were likely similar to conditions
that existed on Earth at about the same time — when early life was evolving
here.”
Today, Mars is a cold, dry
place that experiences no volcanic activity. But roughly 3.7 billion years ago,
the situation was vastly different. At that time, Mars boasted both flowing and
standing bodies of water, which are evidenced by vast fluvial deposits and
sedimentary basins.
The Gale Crater is a perfect
example of this since it was once a major lake bed, which is why it was
selected as the landing site for the Curiosity rover in 2012.
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| Illustrates showing the origin of some deposits in the Eridania basin of southern Mars resulting from seafloor hydrothermal activity more than 3 billion years ago. Credit: NASA |
Since Mars had both surface
water and volcanic activity during this time, it would have also experienced
hydrothermal activity. This occurs when volcanic vents open into standing
bodies of water, filling them with hydrated minerals and heat. On Earth, which
still has an active crust, evidence of past hydrothermal activity cannot be
preserved. But on Mars, where the crust is solid and erosion is minimal, the
evidence has been preserved.
“This site gives us a
compelling story for a deep, long-lived sea and a deep-sea hydrothermal
environment,” Niles said. “It is evocative of the deep-sea hydrothermal
environments on Earth, similar to environments where life might be found on
other worlds — life that doesn’t need a nice atmosphere or temperate surface,
but just rocks, heat and water.”
Based on their study, the
researchers estimate that the Eridania basin once held about 210,000 cubic km
(50,000 cubic mi) of water. Not only is this nine times more water than all of
the Great Lakes combined, it is as much as all the other lakes and seas on
ancient Mars combined. In addition, the region also experienced lava flows that
existed after the sea is believed to
have disappeared.
From the CRISM’s
spectrometer data, the team identified deposits of serpentine, talc and
carbonate. Combined with the shape and texture of the bedrock layers, they
concluded that the sea floor was open to volcanic fissures. Beyond indicating
that this region could have once hosted life, this study also adds to the
diversity of the wet environments which are once believed to have existed on
Mars.
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| A scale model compares the volume of water contained in lakes and seas on the Earth and Mars to the estimated volume of water contained in an ancient Eridania sea. Credit: JJoseph R. Michalski (et al.)/Nature Communications |
Between evidence of ancient
lakes, rivers, groundwater, deltas, seas, and volcanic eruptions beneath ice,
scientists now have evidence of volcanic activity that occurred beneath a
standing body of water (aka. hot springs) on Mars. This also represents a new
category for astrobiological research, and a possible destination for future
missions to the Martian surface.
The study of hydrothermal
activity is also significant as far as finding sources of extra-terrestrial,
like on the moons of Europa, Enceladus, Titan, and elsewhere. In the future,
robotic missions are expected to travel to these worlds in order to peak
beneath their icy surfaces, investigate their plumes, or venture into their
seas (in Titan’s case) to look for the telltale traces of basic life forms.
The study also has
significance beyond Mars and could aid in the study of how life began here on
Earth. At present, the earliest evidence of terrestrial life comes from
seafloor deposits that are similar in origin and age to those found in the
Eridania basin. But since the geological record of this period on Earth is
poorly preserved, it has been impossible to determine exactly what conditions
were like at this time.
Given Mars’ similarities
with Earth, and the fact that its geological record has been well-preserved
over the past 3 billion years, scientists can look to mineral deposits and
other evidence to gauge how natural processes here on Earth allowed for life to
form and evolve over time.
It could also advance our
understanding of how all the terrestrial planets of the Solar System evolved
over billions of years.
Via UniverseToday