NASA rover finds a rock on Mars named 'Skull Hill' that doesn't belong where it was found

NASA’s Perseverance rover has rolled across a bright carpet of dust and bedrock for more than four years, but few sights have stopped the team in its tracks quite like a charcoal‑colored boulder perched on Witch Hazel Hill.

The oddity, dubbed “Skull Hill,” sits alone against tan sandstone, pocked with shallow pits and angled facets.

The rover first photographed the stone on April 11 while crossing a contact where light and dark units meet along the rim of Jezero Crater.

Katie Morgan of NASA’s Jet Propulsion Laboratory (JPL) says that every fresh turn in the rim campaign has produced surprises, and Skull Hill is “all we had hoped for and more.”

Skull Hill interrupts the crater rim

Skull Hill is no pebble; Perseverance rover’s Mastcam‑Z images show a block roughly 1 ft tall and 1.6 ft wide that casts a sharp shadow at noon.

Its basalt‑black skin contrasts so strongly with the surrounding deposits that researchers immediately tagged it as a foreigner to the site.

The Jezero rim preserves a cross‑section of Mars’s crust, making it an ideal place to inventory rock types carried in by rivers, glaciers, or impacts. Each stray clast offers clues to terrains now eroded or buried elsewhere on the planet.

“We’ve found a few of these dark‑toned floats in the Port Anson region,” the mission blog reports.

Mission scientists call such wanderers “floats” because they lie loose on the surface, having been transported far from their birthplace by water, wind, or blast waves. 

How rocks like Skull Hill “float”

Three billion years ago Jezero held a lake nearly 28 miles across, fed by rivers that spilled over its rim and left a fan‑shaped delta now famous in orbital photos.

Floods likely moved cobbles from the crater’s southern highlands into the basin before water vanished.

Later impacts churned up deeper layers and hurled projectiles across the landscape, peppering the delta with foreign stones.

Models show that a 0.6‑mi‑wide crater can scatter ejecta more than 12 mi downrange, easily reaching Witch Hazel Hill.

After the water was gone, aeolian abrasion took over. Ventifacts identified elsewhere on Mars develop when sand‑laden winds grind rock faces, sculpting facets and shallow pits. Skull Hill’s dimples could record the same relentless sandblasting.

Meteorite or volcanic fragment?

At first glance the boulder’s metallic sheen suggested it might be an iron meteorite like “Egg Rock,” which Curiosity zapped in Gale Crater in 2016. Meteorites are rich in nickel‑iron alloys and often survive entry as glossy, fist‑size lumps.

Perseverance tested the idea within hours using its turret‑mounted SuperCam laser. Early spectra showed scant nickel, pushing investigators toward an igneous origin instead.

Dark‑toned units elsewhere in Jezero, such as the Máaz formation, carry abundant olivine and pyroxene, minerals that crystallize from cooling magma.

If Skull Hill is a chipped piece of that volcanic crust, it may have been excavated by impacts or fractured during ancient quakes.

Still, the team has not ruled out a stony meteorite made of chondritic material, which contains far less nickel than iron meteorites.

Ongoing LIBS measurements will refine elemental ratios to better than 5 percent, a precision demonstrated in recent instrument tests.

Tools that read Martian rocks’ DNA

SuperCam fires a five‑nanosecond pulse that heats surface grains to plasma, and detectors then parse the glow to identify elements.

Combined with the rover’s LIBS capability, the system can analyze spots smaller than a pencil eraser from up to 23 ft away.

Chemistry is married to context by Mastcam‑Z stereo imaging, panoramic mosaics, and microscopic color close‑ups that reveal textures as fine as 0.05 in. That detail lets geologists match mineralogy to grain size and erosional features.

“Luckily for us, the rover has instruments that can measure the chemical composition of rocks on Mars,” the operations team wrote.

Perseverance has so far probed 83 targets with its laser on Witch Hazel Hill alone, a record pace for the mission. 

Why does Skull Hill rock matter?

Floats like Skull Hill extend the rover’s reach beyond its wheels. A single exotic sample can point to rock layers tens of miles away, offering a geologic telegram from terrains the rover will never visit.

If the boulder proves volcanic, it could anchor the age of eruptions suggested by orbital mapping of the crater floor. In situ dating with returned samples might then calibrate crater‑count chronologies used across the Red Planet.

A meteorite identification would be equally valuable. Weathered fusion crust, corrosion rinds, and impact pits would reveal how metals rust under Martian climate cycles, information vital for future human hardware.

The pits themselves chronicle present‑day wind power. Models of crater‑slope circulation predict gusts exceeding 40 mph at midday, fast enough to loft sand and abrade exposed rocks.

Mars sample return in doubt

Skull Hill lies only yards from a planned cache site where the rover could seal core samples in titanium tubes for a future pickup.

Yet the Mars Sample Return program faces a shrinking budget and an $11 billion cost cap that Administrator Bill Nelson called “too expensive” in 2023.

NASA has asked industry teams to redesign the mission for launch later this decade while trimming billions from the price tag.

If the schedule holds, tubes dropped in Jezero could reach Earth in the mid‑2030s. Until then, Perseverance will keep trundling along the crater rim, zapping floats and drilling cores. 

The study is published in Communications Earth & Environment.

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