Scientists say Earth and Mars may have formed from the collision of rocks the size of the Moon.
REPUBLIKA.CO.ID, JAKARTA — A recent study shows that there is a possibility Earth and Mars formed from collisions between giant moon-sized rocks, not from clumps of gravel that accumulated over time. Previous research suggests that there may be two main ways in which rocky planet as the Earth is formed.
However, classical study models suggest that moon-sized rocks to Mars, dubbed planetary embryos, were once regularly smashed together in the inner solar system, eventually gathering into full-size worlds.
A newer alternative concept envisions small pebbles from outside the solar system drifting inward toward the sun, until they gradually accumulate to form rocky planets like Earth and Mars. This is a process thought to be important for the formation of the cores of giant planets like Jupiter and Saturn.
To see which model could best explain how the rocky planets in the solar system formed, the scientists analyzed a total of about 0.77 ounces (22 grams) of material from 17 meteorites that came from Mars.
The rocks were flung from Mars by an ancient asteroid impact, eventually finding their way to Earth. The researchers examined how these samples varied in their isotopic composition.
Isotopes are forms of the same chemical element that differ only in the number of neutrons in their nucleus. For example, uranium-234 has 142 neutrons in its nucleus while uranium-238 has 146 neutrons.
The scientists compared the levels of titanium, zirconium and molybdenum isotopes from Mars and from Earth with different groups of meteorites from the inner and outer solar systems. From there, they found Earth and Martian rocks more like meteorites than the inner solar system. Only about four percent of the composition resembles the material of the outer solar system.
The large number of Martian meteorites they analyzed helped overcome conflicting results seen in previous studies analyzing small amounts of these rocks. The study’s lead author, Christoph Burkhardt, a planetary scientist at the University of Münster in Germany, said: “Overall, it resolves the conflicting interpretations of previous research and suggests that Earth and Mars formed from material that comes mostly from the inner solar system.
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