101955 Bennu

At a glance

Key points

Its returned sample contains amino acids, all five nucleobases and sugars.

• Darker than charcoal
• Sample contains all five nucleobases
• 121.6 g of asteroid delivered to Earth in 2023

A loose pile

Bennu's low density means it is mostly boulders and gravel held together by its own feeble gravity, with empty space between. When OSIRIS-REx touched down in October 2020 its sampler sank in as if the surface were a ball pit.

Ingredients for life

Laboratory studies of the sample found amino acids, all five bases used in DNA and RNA, ammonia, and salts left by evaporating brine. In December 2025 researchers reported ribose and glucose, the first glucose found in an extraterrestrial sample.

An active asteroid

Weeks after arriving, OSIRIS-REx caught Bennu flinging pebbles into space. In the largest event, on 6 January 2019, about 200 particles up to roughly 10 cm across left the surface at around 3 m/s; some went into brief orbits and fell back, others escaped. Proposed causes include small meteoroid impacts and rocks cracking as they heat and cool through each 4.3-hour day.

Older than it looks

Bennu's rocks formed about 4.6 billion years ago inside a larger world that a collision later destroyed. Bennu itself gathered from a small share of that rubble roughly 1 to 2 billion years ago, probably in the main belt, before drifting onto an orbit that crosses Earth's. Tracking during the mission, including the gentle Yarkovsky push from heat its surface radiates, sharpened forecasts of its path for the next few centuries. A harmless close pass in 2135 matters most: how Earth's gravity bends Bennu's path then decides where it goes afterwards.

What we still don't know

How much of this organic chemistry was delivered to the early Earth by bodies like Bennu.

Missions

1. 2016–2023

   OSIRIS-REx

   NASACompleted

   Returned 121.6 g of asteroid Bennu to Earth on 24 Sep 2023; continues as OSIRIS-APEX to Apophis.

Related entries

• 162173 RyuguDiamond-shaped asteroid sampled by Hayabusa2
• 99942 ApophisThe asteroid that will skim Earth in 2029

Sources

1. NASA Science: 101955 Bennu (opens in a new tab)
2. Lauretta et al. 2019, particle ejection from Bennu, Science (opens in a new tab)
3. Farnocchia et al. 2021, Bennu ephemeris and hazard, Icarus (opens in a new tab)
4. JPL Small-Body Database: 101955 Bennu (opens in a new tab)
5. NASA: Bennu sample reveals mix of life's ingredients (opens in a new tab)
6. NASA: Sugars, gum, stardust in Bennu samples (opens in a new tab)
7. NASA: OSIRIS-REx insight into Bennu's future orbit (opens in a new tab)

Last reviewed 10 Oct 2026 against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.