{"id":29686,"date":"2022-02-14T13:12:18","date_gmt":"2022-02-14T13:12:18","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=104667"},"modified":"2022-02-14T13:31:12","modified_gmt":"2022-02-14T13:31:12","slug":"asteroid-433-eros-and-the-valentines-day-spacecraft-encounter","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/asteroid-433-eros-and-the-valentines-day-spacecraft-encounter\/","title":{"rendered":"Asteroid 433 Eros and the Valentine\u2019s Day spacecraft encounter"},"content":{"rendered":"

<\/p>

By Jane Williamson\n \t\t<\/p>

Published: Monday, 14 February 2022 at 12:00 am<\/p>

\n\n

Sitting between Mars and Jupiter is the asteroid belt<\/a>, a mess of stony, metallic rubble left over from the formation of the Solar System.<\/p>\n

From fragments just a few metres wide up to 940km-diameter giant Ceres<\/a> (classed as a dwarf planet), the millions of objects in the asteroid belt include thousands whose orbit around the Sun brings them into our neighbourhood.<\/p>\n

In fact, NASA\u2019s latest estimate puts the number of large near-Earth asteroids at over 28,000.<\/p>\n

\""Artist's\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Artist\u2019s impression of an asteroid belt. Credit: Maciej Frolow \/ Getty Images<\/span><\/figcaption><\/div>\n

As these objects have largely remained unchanged over millennia, finding out their size, shape, mass and density, understanding their chemical composition and what their surfaces are like, all give us a crucial window into the earliest days of our Solar System.<\/p>\n

It could also help us understand their role in carrying the ingredients for life and, more dramatically, plan how to deflect asteroids on a collision course with Earth<\/a>.<\/p>\n

\u00a0<\/strong>What makes 433 Eros special?<\/strong><\/h2>\n
\""433\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
433 Eros, as seen by the NEAR spacecraft. Credit: NASA\/JPL<\/span><\/figcaption><\/div>\n

It was 433 Eros \u2013 the first asteroid that humanity landed on \u2013 that gave us our first major answers to some of the most fundamental questions about the Universe.<\/p>\n

Roughly 33 x 13 x 13km in size and resembling a flattened and dented kidney, 433 Eros orbits the Sun every 643 days, with a path that brings it as close as 22 million kilometres from Earth.<\/p>\n

For an interactive\u00a0 3D view of what it looks like, take a look at this NASA page<\/a>.<\/p>\n

The first near-Earth asteroid to be discovered, back in 1898 by German astronomer Carl Gustav Witt, in subsequent decades 433 Eros remained the most constantly studied by ground-based observers.<\/p>\n

This is principally because its predictable orbit helped refine our estimates of how far Earth is from the Sun.<\/p>\n

NEAR Shoemaker meets Eros<\/strong><\/h2>\n
\""Artist's\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Artist\u2019s impression of the NEAR spacecraft orbiting asteroid Eros. Credit: NASA<\/span><\/figcaption><\/div>\n

The Galileo spacecraft<\/a>\u2018s flyby observations of asteroids 951 Gaspra and 243 Ida in the early 1990s got the first peek at two asteroids up close.<\/p>\n

But it was NASA\u2019s NEAR (Near-Earth Asteroid Rendezvous) probe \u2013 later renamed NEAR Shoemaker \u2013 that took asteroid research a huge step forward.<\/p>\n

On board were a near-infrared spectrometer<\/a> to determine Eros\u2019s composition, a multispectral imager, a telescope with a CCD array to determine its size, shape and spin and a magnetometer to measure Eros\u2019s magnetic field<\/a>.<\/p>\n

After a few worrying malfunctions, Shoemaker\u2019s first flyby of 433 Eros was on 23 December 1998 at a speed of 0.965 km\/s and a distance of 3827km, after which followed months of close observations.<\/p>\n

Fittingly, for an asteroid named after the Greek god of love, it was on Valentine\u2019s Day 2000 that Shoemaker fell into orbit around the asteroid, the first ever spacecraft to do so.<\/p>\n

Descending at times as low as just 5.3km above the surface, it continued to capture thousands of high-resolution close-up photographs.<\/p>\n

What NEAR Shoemaker found out<\/strong><\/h2>\n
\""An\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
An image of Eros\u2019s southern hemisphere, where the NEAR Shoemaker touched down. Credit: NASA<\/span><\/figcaption><\/div>\n

After nearly a year and 230 orbits, on 12 February 2001 Shoemaker gently touched down, travelling at just 6.4km\/hr, on the asteroid\u2019s eastern side, next to the large saddle-shaped depression called Himeros.<\/p>\n

For about two weeks the probe continued to return data, but by 28 February all radio communication was lost.<\/p>\n

During its mission Shoemaker had taken 160,000 photographs and mapped the mineral composition of more than 70% of Eros\u2019s surface.<\/p>\n

It discovered that the asteroid had just two medium-sized craters, suggesting its relative youth, and a 20km-long surface ridge.<\/p>\n

Radar revealed a mix of both smooth and rough areas, with ridges, grooves and depressions, its two craters strewn with boulders, some a whopping 100m in diameter.<\/p>\n

\""Craters\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Craters on Eros, imaged by the NEAR Shoemaker spacecraft from a distance of 35 kilometres above the surface. Credit: NASA\/JPL\/JHUAPLNASA\/JPL\/JHUAPL<\/span><\/figcaption><\/div>\n

It had large variations in brightness in its bouldery surface, with high concentrations of silicon, magnesium, iron, uranium, thorium and potassium.<\/p>\n

Its rotation was timed at once every 5.27 hours and it was found to have no discernible moons and no magnetic field.<\/p>\n

Radio science experiments showed the asteroid\u2019s mass, a vital clue to the nature of its interior, and a density similar to Earth\u2019s own crust.<\/p>\n

Shoemaker also provided indisputable proof that small asteroids could have a substantial regolith, a loose rocky and dusty surface layer hinting at the impacts and erosion in its past.<\/p>\n

By the mission\u2019s end NEAR Shoemaker had revealed a treasure trove of physical and geological clues about one of the leftover building blocks of our planets.<\/p>\n

\""Two\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Two similarly sized craters on Eros, captured by the NEAR Shoemaker spacecraft on 1 January 2001 from 35km away. The left crater is a \u2018fresh\u2019 crater with a defined rim. The right crater is older, more degrades and partially buried by regolith. Credit: NASA\/JPL\/JHUAPL<\/span><\/figcaption><\/div>\n

When is Eros\u2019s next close approach to Earth?<\/strong><\/h2>\n

Eros\u2019s next closest approach to Earth will happen on 24 January 2056, when it will be at a distance of 0.14979957 Astronomical Units or 22.4 million kilometres.<\/p>\n

Missions similar to NEAR Shoemaker at asteroid Eros<\/strong><\/h2>\n