Haumea and its moons Hi'iaka and Namaka. Artist's concept by A. Feild, STScI
Let’s all give a big welcome to a newly named (but not newly discovered) dwarf planet orbiting the Sun out between 35 and 50 AU from the Sun. The new name is Haumea, given this week by the International Astronomical Union to honor the Hawaiian goddess of childbirth and fertility. In Hawaiian mythology, this goddess also represents the element of stone, which is very applicable to this dwarf planet. Observations of Haumea hint that this world is almost entirely composed of rock with a crust of pure ice — somewhat unusual for this region of the solar system.
Haumea is joined in its orbit by two satellites that are thought to have been created by impacts with other objects in the distant past, collisions that blasted parts of the surface away from Haumea. The debris likely re-coalesced to form the two moons. The first and largest moon is now named Hi’iaka, after the Hawaiian goddess who is said to have been born from the mouth of Haumea and the patron goddess of the island of Hawai’i. The second moon of Haumea is named Namaka, a water spirit who is said to have been born from Haumea’s body.
Seas on Ancient Mars (artist's conception) (courtesy Mars Polar Lander web site)
There’s no question that Mars had water in the past. The evidence is everywhere, from eroded shorelines and river bottoms to crystals that could only have formed in the presence of water. The big question for planetary scientists (among many) is how long ago that water flowed (and precipitated).
Scientists at the Planetary Science Institute are presenting what they consider to be very strong evidence that flowing water and precipitation helped shape the Martian surface around the Valles Marineris until at least 3 billion years ago — during a period in Mars’s geologic history known as the Hesperian Era.
It’s long been suspected that there was running water on Mars during its first billion years of existence, up to the end of the Noachian era. But, the big question was, did the watery past extend later into Mars history? To answer that, a team of PSI researchers led by Catherine Weitz, studied images from the Mars Reconnaissance Orbiter’s HiRISE instrument and focused in on light-toned layer deposits seen on the plains near the Valles Marineris. It appeared to the team that the light-colored deposits are very different from the ones inside the giant canyon nearby. To a geologist, this suggests that the processes that created the deposits outside the Valles Marineris were different from the ones inside the canyon.
Weitz found light-toned layered deposits that are associated with valley systems and inverted channels in two locations near Valles Marineris. You can see inverted channels on Earth in places where sediment (dirt, sand, and mud) is deposited in a stream bed or river bottom. When these streams dry up, the surrounding, softer terrain erodes away. What’s left behind are harder, cemented sediments in the former streambeds standing above the surrounding terrain.
The team also found valley systems in the area they studied that were probably created by running water in two other areas of light-toned layered deposits adjacent to Valles Marineris. All of these phenomena point toward what geologists call fluvial processes — those associated with running water.
Now, there are other processes such as volcanism or wind deposition (called aeolian processes), that can create light-toned deposits like the ones the PSI team has been studying. However, the material is so distinct from other lighter-colored deposits and is so closely associated with valleys and channels, that it’s not difficult to see where fluvial processes could be responsible. It’s like looking at the remains of an ancient riverbed on Earth and using the deposits to tell the story of past flooding and precipitation activity. To see it on Mars in areas where we know the relative ages of the surface regions and know what rocks and minerals exist there is fascinating and gives us a much clearer picture of the action of water over a longer period in this planet’s history.
