The problem was that the asset I was trying to delete is an ImageCollection! To delete it, one needs first to delete each image individually before deleting the ImageCollection.

To do so in the Java GUI:

1. Click on the asset details
2. Go to Images, delete each image (thrash icon)
3. Then use the Delete button

Alternatively, if one uses the earthengine command line, one needs to pass the recursive argument to rm:

earthengine rm --recursive collection_id

The problem was that the asset I was trying to delete is an ImageCollection! To delete it, one needs first to delete each image individually before deleting the ImageCollection.

To do so in the Java GUI:

1. Click on the asset details
2. Go to Images, delete each image (trash icon)
3. Then use the Delete button

Alternatively, if one uses the earthengine command line, one needs to pass the recursive argument to rm:

earthengine rm --recursive collection_id